Hi, I get the following message when trying to use Thunderbird to send email while connected through my VPN service (IPVanish).
"An error occurred while sending mail: The mail server sent an incorrect greeting: resomta-po-09v.sys.comcast.net resomta-po-09v.sys.comcast.net CSI IP 184.108.40.206 is not permitted to send messages. Please contact support if you feel this is in error.."
This just started happening in the last 2-3 weeks, was working fine before that.
My guess is that Comcast does not want any of their customers using a VPN and is taking measures to discourage such use. I'm also sure that there will be a way to defeat Comcast's efforts soon.
I ended up calling Xfinity/Comcast tech support. I talked to a level 1 person who couldn't help, so he wrote up a ticket to pass to level 2 support. I got a call back from level 2, and the person wanted me to remove the comcast account from Thunderbird, and then add it back. I didn't want to do that without a full backup, so did not take any action. Then last night, I accidently replied to an email without thinking, while still running through the VPN, and - it worked! Has been working all day today also. I haven't changed anything on my system. So I'm wondering if that's coincidence or if some intrepid level 2 support person followed up and actually fixed the problem on their end. In any case, it's working again, so I'm happy :-)