[RndTbl] Gmail problem sending from your own SMTP server

[Gilbert E. Detillieux]

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

-- 
Gilbert E. Detillieux        E-mail:  <gedetil at cs.umanitoba.ca>
Dept. of Computer Science    Web:     http://www.cs.umanitoba.ca/~gedetil/
University of Manitoba       Phone:   (204)474-8161
Winnipeg MB CANADA  R3T 2N2  Fax:     (204)474-7609