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RE: relaying denied



olga urbantimes net wrote:
>> Am Do, den 24.06.2004 schrieb olga urbantimes net um 22:47:
>> 
>>>> 4) Should have a complete list of valid mailboxes for hosty so
>>>> that if an e-mail does come in for mydomain.com on hostsx, it can
>>>> reject it instead of sending a DSN back to a forged address. Thus
>>>> clogging up your mail queue. I do this using LDAP queries, but you
>>>> could create a list of virtual users to compensate.
>> 
>>> Are these valid mailboxes set up in /var/spool/mail ?
>> 
>> No! That is the local mail spool directory. As Steve said you could
>> use /etc/mail/virtusertable (and it's hashed db file).
>> 
> 
> Oh, ok. Then where will the mail message that comes for the domain on
> Y will physically reside? Sorry if I am understanding all parts of
> this clearly.
> 

You can only have one mailbox per domain recipient. You have chosen the
server where the physical mailbox lives (server x). In sendmail terms, local
delivery to a mailbox is defined by adding the domain name to
/etc/mail/local-host-names. But you can also have multiple mail servers
accepting mail for a single domain. i.e. backup MX. So the backup MX server
should not store e-mail (no entry in local-host-names), but rather relay the
e-mail to the primary MX for that domain (relay-domains/mailertable).
Furthermore, the backup MX server needs to know a valid list of mailboxes on
the primary MX prior to relaying. Otherwise if the primary MX accepts a
relay'd e-mail from the backup MX to a unknown user, it will reject it back
to the sender with a DSN. Trust me, most (if not all) spam has a forged
return address. So your mail queues will get clogged with undeliverable
e-mails for days.

Steve Cowles



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