Posting via email gives "Connection refused"

I answered to this post some days ago with an email and the post never appeared online. In the following, an excerpt of the email I sent: if needed I can provide the full original.

To: Al Ghaazi via Silverstripe Forum <>
Date: Wed, 27 Apr 2022 08:33:54 +0200
In-Reply-To: <topic/>
References: <topic/>

This morning an email informed me that message could not be delivered because the connection was refused.

I already have the mailing list mode enabled in my preferences: is there something else I must do to be able to use this forum as mailing list?

It must an issue with SilverStripe replying via email component, hence, your reply wasn’t posted to the initial topic.

This is a discourse issue, it has nothing to do with SilverStripe.