MAIL won't authenticate with the correct email address - uses the FROM address

Expected behavior

Mail should authenticate with the server using the usernames / email address entered in the IMAP and SMTP fields

Actual behavior

If I have a different email address in the main email address field (near the top just underneath the users full name), the system authenticates using that instead against the SMTP server.

Mail app

Mail app version:
0.10.0

Mailserver or service: (e.g. Outlook, Yahoo, Gmail, Exchange,...)
Dovecote / Postfix on Ubuntu 14

Number of accounts: (e.g. 1 or 2)
1 account

Server configuration

Operating system: (e.g. Debian 8)
Ubuntu Server 18.04 LTS

Web server: (e.g. Apache, Nginx,...)
Apache2

Database: (e.g. MariaDB, SQLite, PostgreSQL,...)
MariaDB

PHP version: (e.g. 7.0)
7.2

Nextcloud Version: (see admin page, e.g. 13.0.2)
14.0

Updated from an older version or fresh install:
Fresh today

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your server installation folder
Enabled:
  - accessibility: 1.0.1
  - activity: 2.7.0
  - calendar: 1.6.2
  - camerarawpreviews: 0.5.6
  - circles: 0.15.1
  - cloud_federation_api: 0.0.1
  - cms_pico: 0.9.7
  - comments: 1.4.0
  - contacts: 2.1.6
  - dav: 1.6.0
  - deck: 0.4.1
  - federatedfilesharing: 1.4.0
  - federation: 1.4.0
  - files: 1.9.0
  - files_external: 1.5.0
  - files_pdfviewer: 1.3.2
  - files_sharing: 1.6.2
  - files_texteditor: 2.6.0
  - files_trashbin: 1.4.1
  - files_versions: 1.7.1
  - files_videoplayer: 1.3.0
  - firstrunwizard: 2.3.0
  - flowupload: 0.0.8
  - gallery: 18.1.0
  - logreader: 2.0.0
  - lookup_server_connector: 1.2.0
  - mail: 0.10.0
  - mindmaps: 0.1.0
  - mood: 0.4.0
  - nextcloud_announcements: 1.3.0
  - notifications: 2.2.1
  - oauth2: 1.2.1
  - ownbackup: 18.8.1
  - password_policy: 1.4.0
  - passwords: 2018.9.1
  - phonetrack: 0.3.1
  - provisioning_api: 1.4.0
  - richdocuments: 2.0.13
  - serverinfo: 1.4.0
  - sharebymail: 1.4.0
  - socialsharing_email: 1.0.4
  - spreed: 4.0.0
  - support: 1.0.0
  - survey_client: 1.2.0
  - systemtags: 1.4.0
  - tasks: 0.9.7
  - theming: 1.5.0
  - twofactor_backupcodes: 1.3.1
  - twofactor_totp: 1.5.0
  - updatenotification: 1.4.1
  - workflowengine: 1.4.0
Disabled:
  - admin_audit
  - encryption
  - user_external
  - user_ldap

The content of config/config.php:

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder
{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "caaos-cloud"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "14.0.0.19",
        "overwrite.cli.url": "http:\/\/caaos-cloud\/nextcloud",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_smtpauthtype": "PLAIN",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***"
    }
}

or

Insert your config.php content here
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

Client configuration

Browser: (e.g. Firefox 48)
Chrome and Firefox - uptodate

Operating system: (e.g. Arch Linux)
Arch

Logs

Web server error log

Insert your webserver log here (e.g. /var/log/apache2/...)

Server log (data/nextcloud.log)

2.0) Gecko\/20100101 Firefox\/62.0","version":"14.0.0.19"}
{"reqId":"sEiujqaEdHLCFgEF3inv","level":3,"time":"2018-09-26T16:35:47+00:00","remoteAddr":"192.168.1.124","user":"--","app":"passwords","method":"GET","url":"\/nextcloud\/cron.php","message":"OCA\\Passwords\\Cron\\ProcessDeletedUsers must be executed as cron job","userAgent":"Mozilla\/5.0 (X11; Linux x86_64; rv:62.0) Gecko\/20100101 Firefox\/62.0","version":"14.0.0.19"}
{"reqId":"0e8VLPSnZfIC84dF8Elc","level":3,"time":"2018-09-26T16:36:06+00:00","remoteAddr":"192.168.1.124","user":"--","app":"passwords","method":"GET","url":"\/nextcloud\/cron.php","message":"OCA\\Passwords\\Cron\\ProcessDeletedEntities must be executed as cron job","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"8pCjLQkcs7btjQh7WNUv","level":3,"time":"2018-09-26T16:36:13+00:00","remoteAddr":"192.168.1.124","user":"--","app":"passwords","method":"GET","url":"\/nextcloud\/cron.php","message":"OCA\\Passwords\\Cron\\CheckPasswordsJob must be executed as cron job","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"ChKYtV1XvwzxEfz0fBIN","level":3,"time":"2018-09-26T16:36:19+00:00","remoteAddr":"192.168.1.124","user":"--","app":"passwords","method":"GET","url":"\/nextcloud\/cron.php","message":"OCA\\Passwords\\Cron\\SynchronizeShares must be executed as cron job","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"xbWjaalK3boiX8MH7UgN","level":3,"time":"2018-09-26T16:37:14+00:00","remoteAddr":"192.168.1.124","user":"katherine","app":"mail","method":"POST","url":"\/nextcloud\/index.php\/apps\/mail\/api\/accounts\/2\/send","message":"Sending mail failed: Server is not accepting SMTP connections.","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"xbWjaalK3boiX8MH7UgN","level":3,"time":"2018-09-26T16:37:14+00:00","remoteAddr":"192.168.1.124","user":"katherine","app":"mail","method":"POST","url":"\/nextcloud\/index.php\/apps\/mail\/api\/accounts\/2\/send","message":{"Exception":"Horde_Mime_Exception","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\ReplyMessage"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},18]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,18]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,null,"\n\n\nGary Newbrook \u2013 Wed, 26. September 2018 17:36\n> \n\nWhat, eh?","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",18,"SU5CT1g=",681,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","Line":1642,"Previous":{"Exception":"Horde_Mail_Exception","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","line":1627,"function":"send","class":"Horde_Mail_Transport_Smtphorde","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"From":"Katherine Newbrook <katherine@thenewbrooks.com>","To":"Gary Newbrook <gary@thenewbrooks.com>","Cc":"","Subject":"Re: Test from me","In-Reply-To":"<20180926163634.Horde.9Mt5PgNo20r3QLNIgJNLkkt@caaos-cloud>","Message-ID":"<20180926163714.Horde.WGuOg3uTY7yiTtjMBye6Ed5@caaos-cloud>","User-Agent":"Horde Application Framework 5","Date":"Wed, 26 Sep 2018 16:37:14 +0000","Content-Type":"text\/plain; charset=utf-8","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\ReplyMessage"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},18]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,18]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,null,"\n\n\nGary Newbrook \u2013 Wed, 26. September 2018 17:36\n> \n\nWhat, eh?","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",18,"SU5CT1g=",681,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mail\/Horde\/Mail\/Transport\/Smtphorde.php","Line":145,"Previous":{"Exception":"Horde_Smtp_Exception_Recipients","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Smtp\/Horde\/Smtp.php","line":650,"function":"_getResponse","class":"Horde_Smtp","type":"->","args":[[250,251],{"error":null,"exception":"Horde_Smtp_Exception_Recipients"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mail\/Horde\/Mail\/Transport\/Smtphorde.php","line":143,"function":"send","class":"Horde_Smtp","type":"->","args":[{"comment":[],"mailbox":"katherine","__class__":"Horde_Mail_Rfc822_Address"},{"__class__":"Horde_Mail_Rfc822_List"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","line":1627,"function":"send","class":"Horde_Mail_Transport_Smtphorde","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"From":"Katherine Newbrook <katherine@thenewbrooks.com>","To":"Gary Newbrook <gary@thenewbrooks.com>","Cc":"","Subject":"Re: Test from me","In-Reply-To":"<20180926163634.Horde.9Mt5PgNo20r3QLNIgJNLkkt@caaos-cloud>","Message-ID":"<20180926163714.Horde.WGuOg3uTY7yiTtjMBye6Ed5@caaos-cloud>","User-Agent":"Horde Application Framework 5","Date":"Wed, 26 Sep 2018 16:37:14 +0000","Content-Type":"text\/plain; charset=utf-8","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\ReplyMessage"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},18]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,18]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,null,"\n\n\nGary Newbrook \u2013 Wed, 26. September 2018 17:36\n> \n\nWhat, eh?","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",18,"SU5CT1g=",681,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Smtp\/Horde\/Smtp.php","Line":1058}},"CustomMessage":"--"},"userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"7WuxTM6JGKaBG9KTEYoM","level":3,"time":"2018-09-26T16:38:39+00:00","remoteAddr":"192.168.1.124","user":"katherine","app":"mail","method":"POST","url":"\/nextcloud\/index.php\/apps\/mail\/api\/accounts\/2\/send","message":"Sending mail failed: Server is not accepting SMTP connections.","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}
{"reqId":"7WuxTM6JGKaBG9KTEYoM","level":3,"time":"2018-09-26T16:38:39+00:00","remoteAddr":"192.168.1.124","user":"katherine","app":"mail","method":"POST","url":"\/nextcloud\/index.php\/apps\/mail\/api\/accounts\/2\/send","message":{"Exception":"Horde_Mime_Exception","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\Message"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},19]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,19]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,"Subject","Gary Newbrook \u2013 Wed, 26. September 2018 17:36\n&gt; \n\nWhat, eh?\n\n","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",19,null,null,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","Line":1642,"Previous":{"Exception":"Horde_Mail_Exception","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","line":1627,"function":"send","class":"Horde_Mail_Transport_Smtphorde","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"From":"Katherine Newbrook <katherine@thenewbrooks.com>","To":"Gary Newbrook <gary@thenewbrooks.com>","Cc":"","Subject":"Subject","Message-ID":"<20180926163839.Horde.5CH1xcZxAikeTn5rkR8c7ft@caaos-cloud>","User-Agent":"Horde Application Framework 5","Date":"Wed, 26 Sep 2018 16:38:39 +0000","Content-Type":"text\/plain; charset=utf-8","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\Message"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},19]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,19]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,"Subject","Gary Newbrook \u2013 Wed, 26. September 2018 17:36\n&gt; \n\nWhat, eh?\n\n","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",19,null,null,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mail\/Horde\/Mail\/Transport\/Smtphorde.php","Line":145,"Previous":{"Exception":"Horde_Smtp_Exception_Recipients","Message":"Server is not accepting SMTP connections.","Code":4,"Trace":[{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Smtp\/Horde\/Smtp.php","line":650,"function":"_getResponse","class":"Horde_Smtp","type":"->","args":[[250,251],{"error":null,"exception":"Horde_Smtp_Exception_Recipients"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mail\/Horde\/Mail\/Transport\/Smtphorde.php","line":143,"function":"send","class":"Horde_Smtp","type":"->","args":[{"comment":[],"mailbox":"katherine","__class__":"Horde_Mail_Rfc822_Address"},{"__class__":"Horde_Mail_Rfc822_List"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Part.php","line":1627,"function":"send","class":"Horde_Mail_Transport_Smtphorde","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"From":"Katherine Newbrook <katherine@thenewbrooks.com>","To":"Gary Newbrook <gary@thenewbrooks.com>","Cc":"","Subject":"Subject","Message-ID":"<20180926163839.Horde.5CH1xcZxAikeTn5rkR8c7ft@caaos-cloud>","User-Agent":"Horde Application Framework 5","Date":"Wed, 26 Sep 2018 16:38:39 +0000","Content-Type":"text\/plain; charset=utf-8","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit"},null]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Mime\/Horde\/Mime\/Mail.php","line":479,"function":"send","class":"Horde_Mime_Part","type":"->","args":["Gary Newbrook <gary@thenewbrooks.com>",{"__class__":"Horde_Mime_Headers"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"}]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Account.php","line":214,"function":"send","class":"Horde_Mime_Mail","type":"->","args":[{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},false,false]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Service\/MailTransmission.php","line":116,"function":"sendMessage","class":"OCA\\Mail\\Account","type":"->","args":[{"__class__":"OCA\\Mail\\Model\\Message"},{"send8bit":false,"sep":"\r\n","__class__":"Horde_Mail_Transport_Smtphorde"},19]},{"file":"\/var\/www\/html\/nextcloud\/apps\/mail\/lib\/Controller\/AccountsController.php","line":277,"function":"sendMessage","class":"OCA\\Mail\\Service\\MailTransmission","type":"->","args":["katherine",{"__class__":"OCA\\Mail\\Model\\NewMessageData"},{"__class__":"OCA\\Mail\\Model\\RepliedMessageData"},null,19]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":166,"function":"send","class":"OCA\\Mail\\Controller\\AccountsController","type":"->","args":[2,"Subject","Gary Newbrook \u2013 Wed, 26. September 2018 17:36\n&gt; \n\nWhat, eh?\n\n","\"Gary Newbrook\" <gary@thenewbrooks.com>","","",19,null,null,[],0]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":99,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/App.php","line":118,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Mail\\Controller\\AccountsController"},"send"]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["OCA\\Mail\\Controller\\AccountsController","send",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"accountId":"2","_route":"mail.accounts.send"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"accountId":"2","_route":"mail.accounts.send"}]},{"file":"\/var\/www\/html\/nextcloud\/lib\/base.php","line":989,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/mail\/api\/accounts\/2\/send"]},{"file":"\/var\/www\/html\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/html\/nextcloud\/apps\/mail\/vendor\/pear-pear.horde.org\/Horde_Smtp\/Horde\/Smtp.php","Line":1058}},"CustomMessage":"--"},"userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/69.0.3497.92 Safari\/537.36","version":"14.0.0.19"}

IMAP log (data/horde_imap.log)

IMAP server is fine

Enable debug mode and insert your horde IMAP log here, see https://docs.nextcloud.com/server/13/developer_manual/general/debugging.html#debug-mode

SMTP log (data/horde_smtp.log)

SMTP server is fine

Enable debug mode and insert your horde IMAP log here, see https://docs.nextcloud.com/server/13/developer_manual/general/debugging.html#debug-mode

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 

Start with apps/mail/lib/Account.php at line 214 and trace the send path through Service/MailTransmission.php line 116 and Controller/AccountsController.php line 277. Compare the configured IMAP/SMTP usernames with the From address shown in the log; done means sending authenticates with the account's configured server credentials even when those addresses differ.