Mail server, fully integrated with Nextcloud

Hi,
I have noticed that you already use postfix for sending notification emails ( https://github.com/nextcloud/nextcloudpi/issues/147 ). What about adding full-fledged mail server?

I am a long-time user of Nextcloud (and Owncloud before that). Couple of months ago I have successfully launched an email server (postfix+dovecot+rspamd), FULLY INTEGRATED with Nextcloud. Your email (yourname@yourdomain.com) serves as Nextcloud account. New Nextcloud users automatically get their mailbox. Same login and password for Nextcloud and for email (IMAP and SMTP). You can use webmail in Nextcloud for accessing your mailbox without additional login.

I have followed this excellent tutorial:

https://123qwe.com/

The tutorial is not mine, I am just drawing your attention to it in case you would like to include email server in NextCloudPi. I am on Debian Buster. I have closely followed the tutorial and it works! I would only suggest to use Rainloop app, instead of default Email app. Rainloop has much better UI and does not require additional app "Auto Mail Accounts". As a theme for Rainloop, use https://github.com/LukWebsForge/NextRainCloud .

No project file, test, or entry point is identified. Start by reviewing the linked tutorial and comparing its Postfix, Dovecot, Rspamd, and Rainloop integration with NextcloudPi's existing mail setup; done would require a defined implementation scope and acceptance criteria.