Forum OpenACS Development: Re: AcsMailLite - Lost on debugging
a) acs-mail-lite uses finally tcllib's smtp package
b) you asked, how to debug smtp without OpenACS interference (your formulation "How would I make sure OACS layer is not the guilty". The answer is to call tcllibs smpt package functions via a small script without OpenACS (as indicated in the man page). You can call this script from the shell with any option (look at the options of .::smtp::sendmessage in the manpage). If find a options combination that works from the script, you can check afterwards, how to pass these options via acs-mail-lite. If you find NO combination of options that work, then acs-mail-lite can't do anything, and you have to debug tcllibs smtp.
But since have have fixed out already you misconfiguration, there is no need for going this way.