Comcast filtering SMTP (TCP 25) for IPv6, but 587 still works!

Noticed this weekend that I couldn’t respond to emails on my personal hosted domains. I thought at first first they changed my PD prefix, but it was up to date in Postfix. Tried submission port and it worked just fine. So looks like Comcast finally caught up with “feature parity” in disallowing outbound SMTP connections on TCP 25.

3 thoughts on “Comcast filtering SMTP (TCP 25) for IPv6, but 587 still works!

Leave a Reply