Afterthought about bouncing

Mike Kercher mike at CAMAROSS.NET
Fri Feb 13 13:56:12 GMT 2004

I'm not sure I understand exactly what you're wanting to do, but I'll give
it a shot.

If an email is not deliverable due to an addressing error, your machine
should reject the email connection with a "user unknown".  Your server would
not generate an email to the *sender*.  Their MTA would bounce the message
back to the sender as undeliverable.  This is not any additional load on
your server.  I would leave it up to the sender to make sure the address is
correct before sending...not the postmaster.

If you want to catch all of the mis-addressed emails, add an entry to your
/etc/mail/virtusertable: localuser at

This is called a catch-all.  You could also add a few entries for commonly
mispelled addresses such as:

johndeo at      johndoe at
m.smith at      msmith at


> -----Original Message-----
> From: MailScanner mailing list
> [mailto:MAILSCANNER at JISCMAIL.AC.UK] On Behalf Of Steve Campbell
> Sent: Thursday, February 12, 2004 8:49 PM
> Subject: Afterthought about bouncing
> To the list,
> I really never thought about this until my recent explosion
> of invalid-user emails sent to our domains and my
> undetermined reason for slowness. Could someone explain the
> definition of bouncing to me in their own environment and
> tell me what they think of the below stuff?
> I use a dead box here to capture nonexistent user emails,
> where they are reviewed for simple mis-typed addressing, and
> then either forwarded to the proper user or discarded. I
> blacklist heavily on "From:" to throw away emails.
> In this situation, I hope I am not bouncing much.
> As I research my move to using M4 for pure Sendmail, getting
> away from linuxconf, I have not seen a way to prevent the NDR
> message generated by sendmail when I do not use a fallover
> address (dead box). It appears that this will always occur.
> Isn't this a form of bouncing even though I am not forwarding
> the original message? I want to eliminate as much for MS to
> do as possible, and want to do this at the MTA (SendMail, again).
> Please no wars about bouncing. Just the facts, ma'am. (That's
> from the TV show Dragnet to all of you youngsters).
> Thanks,
> Steve Campbell
> Charleston Newspapers
> campbell at
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