SMTP alt port 465 or 587 ?

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SMTP alt port 465 or 587 ?

Post by jdraggi » Fri Jul 09, 2010 1:45 am

We're in the process of changing our alternative SMTP port from 2500 and making it SSL & TLS.

The question is: Which port would be better to standardize on? And will it make a difference for our users that use SSL or TLS? We'd like to standardize the alternate port and are leaning towards port 465.

I've looked around and have found a lot of discrepancies. For instance:

GOOGLE ... swer=13287 (use authentication)
Use Authentication: Yes
Port for TLS/STARTTLS: 587
Port for SSL: 465

WIKI ... rt_numbers
465 -- UNofficial TCP -- SMTP over SSL & also cisco protocol
587 -- official TCP -- e-mail message submission[10] (SMTP)

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Re: SMTP alt port 465 or 587 ?

Post by brashquido » Tue Jul 13, 2010 3:07 am

I've always used 587 for the alt SMTP port, however if using SSL I'd say you are correct with looking at 465.
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Re: SMTP alt port 465 or 587 ?

Post by trusnock » Fri Oct 08, 2010 4:22 pm

My understanding from RFC4409 ( is that it should use port 587 for "submission", whether you're using encryption or not. Submission refers to a non-public, authenticated port (usually using SMTP-AUTH) that is used for account-holders to submit new messages through.

I can't really determine the story behind port 465 or whether we should be moving toward or away from it. Can anyone clarify this for us?


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