Xfinity SMTP Server

[eirikrrot]

I've been using Listmonk for several months with the same Xfinity SMTP server (STARTTLS, port 587).

But I ran a campaign last night for the first time in a few weeks that failed to connect to the server so I went in to settings to test the server connection and I keep getting this error:

554 resomta-c2p-555694.sys.comcast.net resomta-c2p-555694.sys.comcast.net ESMTP server not available

I tested the SMTP settings with a local, Thunderbird mail client and the connection seems to work there. So the server seems to be up and running.

Has anyone run into this issue over the last few weeks?