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 http://linsec.ca/Using_mutt_on_OS_X to be helpful.
If the above also works for you, please leave a note in the comments below.
Your advice helped me.
Now my mutt on gentoo can send emails via gmail )