> I suspect this has to do with an invalid certification because my test program works fine for sending to gmail.
> ...
> my $s = Net::SMTP::SSL->new('192.168.100.1'...
> ...
> ...SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

I guess your certificate is not signed by any of the trusted CAs on the system. Thus the verification will fail, because there is not trust anchor. In old times (before 1.950, released 07/2013) the default was to not verify the certificate which is of course a bad idea for a default when doing security relevant stuff.