I'm trying to reach some people at a particular ISP (Internet Service Provider), and since I haven't heard from them in some time, sent email to noc@XXXXXXXXXXXXXX, postmaster@XXXXXXXXXXXXXX and root@XXXXXXXXXXXXXX just to make sure that maybe, just maybe, someone there would notice.
I just got this back:
>
```
----- The following addresses had permanent fatal errors -----
postmaster@XXXXXXXXXXXXXX
----- Transcript of session follows -----
... while talking to mail.XXXXXXXXXXXXXX.:
>>> RCPT To:<postmaster@XXXXXXXXXXXXXX>
<<< 550 <postmaster@XXXXXXXXXXXXXX>... User unknown
550 postmaster@XXXXXXXXXXXXXX... User unknown
```
Um … RFC-822 [1] has this to say about postmaster:
>
```
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 "Postmaster@domain" 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.
```
§6.3 of RFC-822 [2]
It's a requirement that postamster exist as a valid email address for any domain accepting email. So the ISP in question is violating an RFC (Request for Comment). Tsk tsk tsk.
[1] http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc0822.html