TLS for SMTP on 465 Fails, but 587 Works

[frankblob]

The setup instructions state that outgoing mails are supposed to go to port 465 (TLS), which never works. Simply changing to 587 (TLS) works. Every time.

It’s the same across several domains, which I all run on Wordpress and handle mail sending via the WP Mail SMTP plugin. I add the password in the wp-config.php and use the correct and full email address. Choosing TLS always fails on port 465, but once I flip to port 587 TLS works, as intended. At least mails go out, and the register at gmail recipients as encrypted, so I assume 587 is doing its job.

Is there a reason that 465 is recommended in the mail setup instructions for TLS?

[Jarland]

In this case it will be an issue on the client side and while I can theorize on the possibilities, I may not be able to know the right answer. These are the first that come to mind:

1. Client-side firewall/network blocking or redirecting traffic on port 465.
2. Out of date SSL libraries attempting to connect using insecure ciphers (seems highly unlikely in this case).
3. Software not able to make direct TLS connection properly, working better with STARTTLS instead (front-end wording not necessarily stating what it is doing in it’s code).