> Am I correct in my understanding that mailers should be sending
> bounces to the From address from the envelope (or to be more precise,
> the address specified in the MAIL FROM: line in the SMTP interchange)?
> Am I also correct in my understanding that this address is the one
> displayed on most Unix sendmail-based systems in the "From<space>"
> line that delimits mail messages?
Usually. However, since some user agents use that field for replies,
some delivery agents put a different address in that field.
> Assuming I'm correct, I am considering not allowing folks to
> subscribe to my lists if their mailer doesn't send errors back to
> the correct address. (I have little tolerance for bounces.) I would
> just build up, manually, a list of host names that don't follow the
> spec. If someone with one of the hostnames tried to subscribe, they'd
> get back a message saying something like, "I know it's probably not
> your fault, but we don't allow non-RFC compliant mailers to use our
> lists. Please have your postmaster contact ______ when it's fixed,
> blah, blah, blah."
> Questions: Has anyone taken this extreme step? What are the possible
I take somewhat less extreme measures. When someone wants to subscribe to one
of my lists using an address that looks like the name of a sub-list, I first
send that person a message asking if the sub-list sets the envelope address
properly. If not, I try to help them fix their mailer.
I have only occasional problems with bounces going to any of my lists, and
the usual culprit is a gateway to a non-Internet mail system which doesn't
keep separate header/envelope addresses.
Then again, my lists don't reset the From header field, so broken mailers will
bounce messages to the sender of the message instead of the list. That's far
from ideal, but at least it doesn't trash the entire list.