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Subject: Re: How to with Virtual Domains
From: Rask Ingemann Lambertsen (rask-postfixkampsax.k-net.dk)
Date: Wed Sep 06 2000 - 11:30:13 CDT

Den 06-Sep-00 16:33:51 skrev Vivek Khera fĝlgende om "Re: How to with Virtual Domains":
>>>>>> "RH" == Ralf Hildebrandt <news-list.postfix.usersinnominate.de>
>>>>>> writes:

RH>> On 6 Sep 2000 11:15:40 +0200, Rask Ingemann Lambertsen
RH>> <rask-postfixkampsax.k-net.dk> wrote:
>>> You _must_ have a postmaster address for all your domains. I.e. for any
>>> virtual domain example.com, you must have two lines in your virtual map:

RH>> Perhaps this should go to the FAQ!

   I think it should. I was certainly very surpriced about one particular
domain which I found didn't have a postmaster address.

>While it is a good idea to do so, it is not _required_ to be there.
>The only thing that I recall seeing as being required is that
>postmasterfqdn.of.mail.server exists, not anything about postmaster
>of any virtual domains hosted by that server. Please point out where
>this is required.

   Virtual or not, it is a domain. How it happens to be implemented at your
end is your problem.

   The requirement for a postmaster address comes from RFC 822 section 6.3:

     6.3. RESERVED ADDRESS

          It often is necessary to send mail to a site, without know-
     ing any of its valid addresses. For example, there may be mail
     system dysfunctions, or a user may wish to find out a person's
     correct address, at that site.

          This standard specifies a single, reserved mailbox address
     (local-part) which is to be valid at each site. Mail sent to
     that address is to be routed to a person responsible for the
     site's mail system or to a person with responsibility for general
     site operation. The name of the reserved local-part address is:

                                Postmaster

     so that "Postmasterdomain" is required to be valid.

     Note: This reserved local-part must be matched without sensi-
            tivity to alphabetic case, so that "POSTMASTER", "postmas-
            ter", and even "poStmASteR" is to be accepted.

   When RFC 822 was written, the word "site" wan synonymous with "domain".
A few years later, the DNS was introduced and with it came MX records,
which meant that a mail domain was no longer necessarily also a host name.
Perhaps some nitwit thought that mail.example.org being MX for example.org
only had to accept mail to postmasterexample.org, not also
postmastermail.example.org. RFC 1123 section 5.2.7 adds this requirement:

      5.2.7 RCPT Command: RFC-821 Section 4.1.1

         A host that supports a receiver-SMTP MUST support the reserved
         mailbox "Postmaster".

   Maybe this clarification confused people to think that the postmaster
requirement was only for the mail host and not the mail domain, maybe it
didn't. In any case, RFC 2142 section 1 says this about reserved addresses:

   The scope of a well known mailbox name is its domain name. Servers
   accepting mail on behalf of a domain must accept and correctly
   process mailbox names for that domain, even if the server, itself,
   does not support the associated service.

   So for mail.example.com configured as MX for example.com,
mail.example.com must support postmasterexample.com and
postmastermail.example.com.

   The only possible unclear part is whether the Postmaster requirement
from RFC 1123 section requires case insensitive matching of Postmaster.
However, I can't express how unwise I think it would be to use case
sensitive string comparison in this case.

Regards,

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