Folks, I might be wrong, but I think we are kinda missing the point in this discussion. As was mentioned before, the SMTP system operates in a store and forward mode, and you can never be sure of the arrival of the message just because the SMTP server in front of you accepted it for delivery However, once the SMTP server has accepted it for delivery, the SMTP system will make every efort to notify the sender in case of failure, whereas if the SMTP server rejects some recipients, it is Zope's responsibility to notify the user. So I think that we should be configuring the SMTP server Zope talks to to accept all e-mail for delivery and check later, so that the sender be notified of failures, otherwise we end up dealing with a maze of possibilities for defining success or failure in Zope. Just my 2 cents Cheers, Leo