Mail authentication error?

[Gordon Messmer]

Hongwei Li wrote:
> 
> Recently, users say that they cannot use Outlook to send emails out if they
> set SSL connection with port 587 for outgoing server and 993 for incoming
> server.

Port 587 isn't an "SSL" port.  It's the MSA port, and probably supports 
TLS.  If Outlook is configured to do SSL rather than TLS, it's not going 
to work.

Port 465 is the SMTP "SSL" port.