I'm trying to send an email based on an attribute, in other words, a lookup and not $user_email of the author.

For instance, if I set a an attribute "Assignee" with a valid user full name (i.e. John Smith), I'd like to look up John Smith's 
email address from the password file and send him an email. I can't seem to find it something like that in the docs, I can write 
a script to do that, but was looking for a less cumbersom way of doing it. Thanks in advance.