Most mail systems use SMPTS instead of SMTP.
The just-included SMTP Service forces using SMTP, even though the JavaMail library allows many different protocols.
At least, support for SMTPS should be included, or, more general, the ability to specify the protocol to use.
Committed as rev. 12276.
I have set the "fix version" so that I appears in Greg's filters. Please, Greg, change that if you think it's not appropriate.
Merged into 1.4.x with rev 12528.