Hey guys, I have some more info as to what we're trying to accomplish. I recently came across the ruby-ntlm gem and installed it. Then, I took a look at the example smtp.rb which uses NTLM to authenticate against a SMTP server (running on IIS that's connected to a NT4 domain) and it works great. However, I've not been able to figure out how we could pass the actual domain name without relying on the domain of the SMTP server for which we're authenticating against. For example... User1 is on Domain1. User1 logs into our app with their username/ password that's defined on Domain1 and get successfully authenticated. User2 is on Domain2. User2 logs into our app (using the same SMTP host - remember, this SMTP server is joined to Domain1) and is unsuccessful at authenticating. Ultimately, we would like to be able to pass "Domain2\User2" as the username and have the ruby-ntlm gem authenticate this user. Another colleague and I have dove into the ntlm.rb (ruby-ntlm's main file) via the debugger and it seems to only be getting the domain from the SMTP host which is being used for the authentication. In essence, does anybody know how to pass the domain of the user being authenticated to ruby-ntml so we can have our multi-trusted domain users authenticate against a single SMTP server? Thanks!