Tuesday, May 21st, 2024 9:28 PM

How to unblock port 25 for Microsoft 365 email

I saw another post that said @XfinityCSAEmail could help with unblocking port 25 for me.  I am using Microsoft 365 Exchange email.  After enabling 2 Factor Authentication on my Microsoft account, I have found that some 3rd party applications can no longer send emails.  I followed Microsoft's recommendations to set up an SMTP Relay connector in Exchange, but it requires being able to send email using port 25.  It will not accept any other port.  

Hopefully someone can help me with this.



Official Employee


988 Messages

22 days ago

Hello @rick6612, Thanks so much for taking a moment out of your day to leave a post on our community forum. Email is used for important communications and Comcast wants to ensure that these communications are as secure and as private as possible. As such, Comcast does not support port 25 for the transmission of email by our residential Internet customers. Much of the current use of port 25 is by computers that have been infected by malware and are sending spam without the knowledge of the users of those computers. I hope that answers all your questions. 

3 Messages

I know that is the standard response, but I have read elsewhere that Comcast will allow using port 25 where it is necessary, as it is in my case, to be able to use Microsoft Exchange Online SMTP Relay functionality.

Official Employee


1.2K Messages

I dearly apologize @rick6612. Currently, port 25 is blocked for all residential customers. While there may have been a process to enable access for some customers in the past, there is not a way to provide access to it at this time.

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30.5K Messages

18 days ago


In addition, residential email does not use the Microsoft Exchange server

3 Messages

@Again​ "residential email does not use the Microsoft Exchange server"   What does "residential email" mean?  There is no such thing as "residential email. " Residential users can use Microsoft 365 email accounts and Microsoft Exchange Online.  Microsoft offers email services to anyone who is willing to pay for them.  Do you think residential users can only use AOL or Yahoo! for email?


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