Emails of Nextcloud users are not included when creating new emails

Steps to reproduce

We are running a nextcloud installation with only the files and mail apps. (Not contacts, talk and circles). When creating a new email, nextcloud users are not available. This can be fixed by setting a core app preference "shareapi_allow_share_dialog_user_enumeration" to yes directly in the database. Then it works, but I do not expect this to be the correct way to enable/disable this function.

Expected behavior

The behaviour should be possible to select, or the default of shareapi_allow_share_dialog_user_enumeration should be yes and not no.

Actual behavior

Nextcloud user emails are not available when creating a new email

Mail app version

No response

Mailserver or service

No response

Operating system

No response

PHP engine version

None

Web server

None

Database

None

Additional info

"core" parameter "shareapi_allow_share_dialog_user_enumeration" should default to "yes" if not available.

No file or test is named in the report. Start by tracing how the Mail compose recipient lookup uses the core preference shareapi_allow_share_dialog_user_enumeration, then check the related Nextcloud configuration path. Done means Nextcloud users' email addresses appear without manually changing the database, with the intended default or selection behavior covered by a test.