Net::SMTP would be a lowest-common-denominator approach, as this is an implementation of the raw SMTP protocol in Perl. It does not rely on an external program to deliver the mail.

There is also (as mentioned in the post I referenced) Mail::Mailer, which is an attempt to make the process of e-mailing totally generic across operating systems and methods. If you're under Unix, telling Mail::Mailer to use 'mail' or 'sendmail' will use the appropriate commands to deliver the mail via the standard system mail delivery mechanism. Telling it to use 'smtp' is equivalent to making it use Net::SMTP. Aside from that the interface is standard and generic.

There's also Mail::Sender (abstracted, yet redundant with Net::SMTP), Mail::Sendmail and Mail::Send. Perhaps others. A simple search against CPAN for mail pulls up a lot. Most of these bill themselves as being platform-independent.