I will check this in an hour

First of all, thanks for reporting and sorry for this issue caused by Wikimedia CH.

Since I do not absolutely remember how the mailbox was managed, I've re-explored the thing a minute.

Hoping to be useful I've added some useful information in our usual documentation page, in a new section called "Mail"

https://meta.wikimedia.org/wiki/Wikimini/Technical_documentation

I've also linked that page from the LocalSettings-secret.php file in the section about $wgSMTP so to be less lost again with undocumented things.

Having said that, it seems the password was reset some time ago by the kind Ilario Valdelli for security reasons. So, I've updated the private configuration file with the new password.

Can you try again? Is it working now?

The situation is not optimal and we have great margin of improvement but at least now it works again. This is just a temporary fix: I've asked to create a dedicated mailbox just for your project, with "wikimini <at> wikimedia.ch" (instead of "mediawiki <at> wikimedia.ch"). So we will change this again, and re-verify this later.)