smtp port

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a viewer

Well-known member
Sep 30, 2020
Just found something interesting today. The SMTP port does more than send the emails, it allows you to chose which protocol you want to use. Used to be some ports were blocked by some ISPs. Port 465 establishes an SSL connection, while 587 does it through TLS (at least with the servers I tried, including gmail). Always thought it was just for convenience or some other historical reason, that we had some extra ports. I know the use of 465 is shun upon, but too many people are still using it. So not sure it will be discontinued soon.

Is there an advantage to using one over the other? Don't know if email programs would disable the obsolete tls versions, or that it would require strong ssl.
Port 465 was originally defined for SMTP over SSL, but has since been reallocated. The one that you should use is 587. That is the port that should be used to send mail from a client, e.g. Outlook or Thunderbird, to a server. Port 25 is meant to be for server to server traffic which is why some ISP's block it.
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