All Google services around the world are currently down: https://www.google.com/appsstatus
Since our phpBB forums use Googles SMTP server, forums mails are currently not delivered, which means that as well registration verifications mails do not arrive.
The quest to setup an own mail server gets higher priority 
.
Update: Google services are back up.
uhh an own mail server could be a challenge. At least to get trusted by other mail relay and not being detected as SPAM 
How about adding an MTA/MDA package in dietpi as well?
I used to run citadel, now moved to postfix/dovecot/rainloop.
Google servers are back up 
!
Yeah, the “trusted by others” was the actual reason why I never had a closer look into it, until a nice step-by-step guide was shared that at least states to accomplish exactly that, if I understood everything right: https://123qwe.com/
That one is with Nextcloud integration, but that can be skipped.
Overview - ISP Mail Tutorial (Caramel Edition)
- Postfix forwards the e-mail to Rspamd which adds a signature (DKIM) to “vouch” that this e-mail is coming from a legitimate mail server.
I need to read inside this a bid and probably get in touch with author and users, to assure that it will be accepted by major mail providers, before starting with it.
I was having an eye on msmtp once in combination with alert mails when drive space is getting close, undervoltage detected, full RAM/OOM and such. A very lightweight solution, good for scripting, but likely not supported OOTB by many applications (but sendmail compatible).
msmtp looks nice too. It would be nice to have some emails from cronjobs, like there are from -arr programs.
Here the related feature request: https://github.com/MichaIng/DietPi/issues/2663