I also use the email address and mailbox managed by Cloudron. Besides sending emails, I also want to process bounces with Listmonk (via pop3). But to make it work, I have to open the terminal to get the credentials via printenv for the incoming mailbox. Do the credentials created by Cloudron stay the same, or do they change over time? Is there a better way to do this?

Thanks!

So it seems that (for now at least) a campaign must have the FROM address as the app mail address. At least the same actual address, but the "friendly name" can be changed. Which is good.

Good points. So, if you let Cloudron manage the email address, then you have to change it from Cloudron Dashboard -> App -> Email -> From address setting. This will fixup the config accordingly. You can also change the setting there to have Cloudron not manage the email at all (if you want to relay using some other provider from inside listmonk).

The name is not configurable but it should be, will fix the package (or the box code).

I did restart the app a few times, but maybe changed the mail password before trying another send.

The fact that restarting the app re-inject the credentials may also explain why an alternative config got deleted.
Bit strange because other settings persist.

Restarting then produced another message in the campaign.
UI allows you to customise the FROM address .... but if it is not the app mail address, there is a different failed authentication error.
So it seems that (for now at least) a campaign must have the FROM address as the app mail address. At least the same actual address, but the "friendly name" can be changed. Which is good.
But it should not suggest that the mail address can be changed.
I appreciate that is an upstream issue, not Cloudron.
Maybe just need to document this.

Anyway, SOLVED ! Thank you @girish.
Now I can explore further.

The SMTP default settings are also correct. Port 2465 is the internal SMTPS port (https://docs.cloudron.io/packaging/addons/#sendmail). Go apps don't work without TLS even if it's all totally internal (which is why we have this semi-deprecated SMTPS port in the first place).

Just to double check, can you restart the app? Restarting the app will re-inject the up to date SMTP credentials. I did try to send a mail campaign before I published and it did work.

But /run/listmonk/config.toml is zero-length file.

Is that ok ?

Whatever I try, I get :
2022/05/31 11:28:30error sending message in campaign Test campaign: subscriber 86eeee23-7dc5-4112-b237-c2967d78f340: 535 5.7.8 Authentication failed
Or in some test configs connection refused

I might trash it and start over.
But what password should be used for the mail host ?
I thought the password for the Cloudron email user (Cloudron admin) but doesn't seem to be so.
So I tried Listmonk admin but no joy with that either.

I changed the password to the one I set for the admin of the app.
And tried my cloudron admin password.
Neither work.
Password field always resets to showing 8 stars ********
Maybe just a default display but makes me suspicious whether the password change is being put into effect.

Buy hey, I've probably screwed it up along the way with my trial & error testing.