On 2020-04-20 11:10 a.m., Hartmut W Sager wrote:
Quoting from the "solution":
It is rare, but it is possible that the server will use a different
certificate on different ports, so switching between 465, 587 and 25 might yield better results. Again, the best source for the settings is your email provider.
In our case, the exact same certificate is used, regardless of which port the connection comes in on. I suspect that would be true for just about anyone, except for some weird cloud hosting providers, maybe...
I tested both 465 SSL and 587 TLS right after encountering the solution, and they both work, though I am under the impression that Gmail favours TLS (whereas I've hitherto always been using SSL). Any thoughts on that?
I don't think it makes any difference, really. (YMMV, depending on server software used.)
Note that here the distinction in terminology between SSL and TLS is simply that the "SSL" port negotiates the encryption right on open, rather than after the client issuing a STARTTLS command, which is the case with the "TLS" port.
This is not referring to protocol versions. These days, all actual SSL protocol versions are obsolete, and should not be used. Even older TLS versions 1.0 and 1.1 should now be avoided. This is configured separately, and should be independent of the port used to connect.
Gilbert