RFC6409 and Port 25 Unblock for MTA

@XfinityCSAEmail 

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.