3 Messages
RFC6409 and Port 25 Unblock for MTA
Hello folks,
I'm not having success over the phone requesting an unblock of port 25 on my internet service. Well-intentioned agents read the same script about port 587. This shows a lack of understanding around how email foundationally moves about the internet and the RFC memo which splits message submission from message relay, RFC6409. To check my own understanding:
- Email messages move from the sender's Mail User Agents (MUAs, should submit on port 587) to...
- Mail Submission Agents (MSAs, should listen on port 587 and must relay on port 25) to...
- one or more Mail Transfer Agents (MTAs, must listen on port 25 and must relay on port 25) to...
- Mail Delivery Agents (MDAs, must listen on port 25 and should accept sessions on port 993, 995, etc.) to, at last...
- the receiver's Mail User Agent (MUA, which should start sessions with their MDAs on port 993, 995, etc).
Port 25 is a must because, from RFC8314:
"SMTP transport MX infrastructure has no way to specify a port, so port 25 is always used."
May I please have port 25 unblocked so my MTA can operate properly? Thanks.
BruceW
Gold Problem Solver
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26K Messages
3 months ago
It seems unlikely for residential service. Please see the discussion in https://forums.xfinity.com/conversations/email/66a01c7ed917b4660c29935c, especially the user_ff4e3544 comment that says an email from Comcast stated:
Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.
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XfinityDena
Official Employee
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2.5K Messages
3 months ago
Thank you for reaching out @user_ra02kb At this time Port 25 is blocked for all residential customers.
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