It would be good to be able to define the sender that
gets put to email reports. We would only need to add
new (optional) line to tw.cfg, like 'MAILFROM =
email@example.com' and the check if it exists.
Normally we don't need this but sometimes there's
machines which don't return reasonable data from
hostname and then the mailer on the other end refuses
the mail (i'm talking about a situation where you
either have no control of the mailserver or other
reasons to not reconfigure it other way).