If you are trying to set up nbSMTP to work with GMail (for example, to get mutt working on OS X), you can
use the following in your .nbsmtprc file:
relayhost=smtp.gmail.com
fromaddr=__YOUR_GMAIL_ADDRESS__
auth_user=__YOUR_GMAIL_ADDRESS__
auth_pass=__YOUR_PASSWORD__
port=587
use_starttls=True
Those of you who are interested in getting Mutt working on OS X might find Using mutt on OS X to be helpful.
If the above also works for you, please leave a note in the comments below.