I was getting an error:
[Tue Nov 20 15:46:17 2001] register: Can't call method "mail" on an undefined value at ../lib/TWiki/Net.pm line 172.
As metioned in: NetSMTP thisoccurs because of a problem
in talking to the SMTP server. In my case it was rejecting me because my host didn't do an EHLO with a fully qualified domain name
.