thank you guys for taking the time to explain things. I see why it's
an issue.
On Sep 27, 2009, at 3:51 PM, Ansgar Wiechers wrote:
On 2009-09-27 Erick Calder wrote:
On Sep 27, 2009, at 1:03 PM, LuKreme wrote:
On Sep 27, 2009, at 2:52 AM, Erick Calder wrote:
On Sep 27, 2009, at 12:53 AM, LuKreme wrote:
On Sep 27, 2009, at 0:53, Erick Calder <[email protected]> wrote:
if the message were for [email protected] then it gets rerouted
to [email protected] which also doesn't exist and therefor bounces.
Yes, it bounces. This makes you a backacatter source. This is bad.
but doesn't my postfix server bounce by default when receiving a
mail
for an inexistent address? and if it doesn't, how are users who
misspell my address to know their message didn't get delivered?
No, not generally. Unknown users are REJECTed, not bounced.
ok, I'm not getting this. your statements of 12:53AM and of 1:03PM
seem contradictory... if an address doesn't exist, does it get
bounced
(as stated on 12:53AM) or rejected (as stated on 1:03PM, in which
case
I'm _not_ a backscatter source, and with which Ansgar and mouss seem
to agree)?
You're just misunderstanding how virtual alias maps work.
During the SMTP dialog Postfix checks its various recipient/relay maps
for valid recipients. If a valid match is found, the mail is accepted
and queued for further relaying. However, Postfix does not expand the
virtual alias maps at this point. If you have a match on the left side
of your virtual aliases, Postfix does not check whether the
corresponding right side entry actually is valid.
Basically the process goes like this:
- Sending MTA starts SMTP dialog, giving [email protected] as the RCPT
TO address
- Postfix finds mapping [email protected] -> [email protected] in its
virtual
alias maps
- Postfix accepts the mail and queues it for further delivery,
because a
valid mapping exists
- Next Postfix tries to relay the already accepted mail to
[email protected],
which is rejected, becaus [email protected] doesn't exist
- Postfix thus finds itself unable to deliver the mail accepted for
[email protected], and thus (as per RFC 2821) MUST generate a bounce
That's why you want to accept mail only for valid addresses.
Regards
Ansgar Wiechers
--
"Abstractions save us time working, but they don't save us time
learning."
--Joel Spolsky
