Fedora List Bounces?

[James Wilkinson]

Mike McCarty wrote:
> Lately I've been getting messages sent by fedora-list-bounces at redhat.com
>
> I'm subscribed to fedora-list at redhat.com, and it seems that
> some send to something, and fedora-list-bounces at redhat.com
> is forwarding it to the list. What gives?

In case it’s not obvious, sending non-delivery “bounces” to the envelope
sender¹ is still common (although it’s falling out of favour due to spam
abuse²).

If these bounces went to fedora-list at redhat.com, then they would either
be sent to the list, or to the (usually ignored) moderation queue. If
the envelope sender was blank (which is allowed), then there would be no
bounces, and the mailing list software couldn’t tell that the e-mail
hadn’t been delivered. So the mailing list software sets the envelope
sender to fedora-list-bounces at redhat.com, and analyses incoming e-mail
to that address to see if it’s a bounce from something it sent out.

An e-mail address that always bounces can and should be removed from the
list.

Hope this helps,

James.

¹The envelope sender is a completely different animal to the “From:” or
“Sender:” address in an e-mail’s headers. It may show up in the “Return
Path” header, or the “From ” line (no colon) that is the very first line
in some mail formats.

²Spammers often set the various “from” addresses to real (but forged)
addresses to get past various ill-considered “anti-spam” measures that
check that e-mail to the sending address will be accepted.

That means that if a server accepts e-mail, then decides it won’t
deliver it (for example, because the recipient exist doesn’t exist),
and bounces the message back to the alleged sender, then the
impersonated sender gets to deal with the spam. This is known either as
backscatter or outscatter. 

The preferred option these days for mail servers is to check for
viruses, spams, and address validity before the e-mail is accepted in
the first place, and then reject the e-mail during the initial SMTP
session. That way real sending servers can generate a bounce for the
(hopefully local) sender.

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