Are you sure you talk to an SMTP server which talks SSL directly?
There are two ways to do SSL within SMTP, one is to just tunnel SMTP within an SSL connection (this is what Net::SMTP::SSL supports) and the other is to have a normal SMTP server (usually sitting at port 25), start a unencrypted session and then switch with STARTTLS command to an SSL session. This is unsupported by Net::SMTP::SSL.
If you are sure that you try to use Net::SMTP::SSL in the intended way (tunnel SMTP through SSL instead STARTTLS on plain connection) you could post an example program which shows your problem (please with the real server) so I could have a look at it.
-- Steffen