Sep 19, 2018

SMTP Port 25, 465 or 587 – How to choose SMTP Port

Port 25 is the default port used for relaying

Port 587
You should use port 587 as default SMTP port. Almost all mail servers support this port.

Port 465

Don’t use port 465, because this port is no longer an accepted standard for SMTP. By the end of 1998, IANA has reassigned this port number for a new service. 

To summarize,
– SMTP port 587 is one of the best choices for nearly every use case.
– Port 465 should no longer be used at all