was this happening to GMAIL and Yahoo or any other SMTP services using the same network? No?
I've never seen an ISP with a mailserver apps.______.com? (I suppose if you were right and it only affected the ISPs own server, that hostname alone could help identify the company involved)
My T-Mobile UK link clearly indicated that T-Mobile UK had been doing it to every SMTP server:
"This isn't just for my mail server, I experienced the same problems using smtp.gmail.com as well," said Cardwell.
and additional comments indicated that moving the server to different ports did not fix the issue because T-Mobile UK was using packet inspection to determine what kind of connection was in use and blocking based on that, not simply based on port. My mistake though, it looks like T-Mobile UK was using a Sandvine-style RST attack (like Comcast used to shut down Lotus Notes and Bittorrent users) to shut down the connection rather than Cisco-style packet rewriting just to disable TLS, so I'm probably wrong about it being T-Mobile. I agree that we should have gotten the name of the ISP so that those of us who require encryption for medical records, legal records, national security reasons, etc would be aware of the potential problem.