Question from customer via email:
asked Jun 14 '12 at 08:56
To answer this question, it's best to spend about two minutes to quickly understand the basics of the SMTP protocol. It's very easy:
The SMTP protocol works like this:
There are two ways to specify the "Return-Path" (i.e. the email address passed in the "MAIL FROM" command within the SMTP protocol.
1) If sending email by passing an email object to a method such as mailman.SendEmail, then set the emailObject.BounceAddress property. This is the address passed in the "MAIL FROM" command. If BounceAddress is unset, then the email object's From address is used.
2) If sending email by passing the exact MIME string, such as via mailman.SendMime, then the "fromAddr" argument is used.
A Note about BackScatter:
Now that you understand Return-Path, you can understand a problem called BackScatter. When a spammer sends millions of emails, the scoundrel will often pass a real email address (harvested from a web page) to the MAIL FROM command. A certain percentage of those emails are (of course) sent to invalid email addresses. A mail server managed by someone without a good understanding SMTP might configure the server to send DSN's (Delivery Status Notifications) for all undelivered emails. The end result is that the unlucky email address used by the spammer gets mail-bombed with DSN's. A good mail server administrator should either turn off DSN's, or only send DSN's for email known to NOT be SPAM.