Postmaster 'best practices' query
A query to help educate me. Feel free to flame away; the week is young. Every site should accept/respond to "postmaster" -- T/F? Or is it "Every site running mail".... Or every box running mail? IOW: Which of the following are required vice recommended vice best practives, etc. a) postmaster@example.com b) postmaster@mail.example.com c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com and most important to me: where to I go to justify the decisions on same? -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
On Mon, Oct 22, 2001 at 10:33:56AM -0400, David Lesher wrote:
Every site should accept/respond to "postmaster" -- T/F?
Or is it "Every site running mail".... Or every box running mail?
IOW: Which of the following are required vice recommended vice best practives, etc.
a) postmaster@example.com b) postmaster@mail.example.com c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com
and most important to me: where to I go to justify the decisions on same?
RFC823 section 6.3, postmaster@ must be valid for all domains accepting mail. Something I've had to quote a lot. -- Ryan O'Connell - CCIE #8174 <ryan@complicity.co.uk> - http://www.complicity.co.uk I'm not losing my mind, no I'm not changing my lines, I'm just learning new things with the passage of time
IOW: Which of the following are required vice recommended vice best practives, etc.
a) postmaster@example.com b) postmaster@mail.example.com c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com
and most important to me: where to I go to justify the decisions on same?
2821 (section 4.5.1) says that "postmaster" (with no domain" must be accepted as: (a) a local name (with no domain specified, as in: RCPT TO:<Postmaster>" (b) A mailbox at every domain for which the mail server accepts mail. That means that the answer to your five questions are are: a) postmaster@example.com is required if any mail addressed to @example.com is accepted. b) postmaster@mail.exam is required if any mail addressed to @mail.example.com is accepted. c), d), e) follow the example above. Had you also included: f) postmaster The answer would be "yes, that is required". RFC2821 would be a good place to go to justify decisions on same. (Well, to justify a decision to implement postmaster@any.domain.for.which.mail.is.accepted, and to implement "postmaster". It wouldn't really help you justify a decision to not implement that. OTOH, if someone is arguing that the the mere existance of xyz.com implies that postmaster@xyz.com must exist, then I would note that neither RFC2821 nor any other RFC of which I am aware imposes such a requirement. As long as @xyz.com isn't being used for any mail, there is no requirement for postmaster@xyz.com to exist.) -- Brett
On Mon, Oct 22, 2001 at 12:02:09PM -0500, Brett Frankenberger wrote: [snip]
RFC2821 would be a good place to go to justify decisions on same. (Well, to justify a decision to implement postmaster@any.domain.for.which.mail.is.accepted, and to implement "postmaster". It wouldn't really help you justify a decision to not implement that. OTOH, if someone is arguing that the the mere existance of xyz.com implies that postmaster@xyz.com must exist, then I would note that neither RFC2821 nor any other RFC of which I am aware imposes such a requirement. As long as @xyz.com isn't being used for any mail, there is no requirement for postmaster@xyz.com to exist.)
Some country-TLD registrars do have this requirement, however. Greetz, Peter -- Monopoly http://www.dataloss.nl/monopoly.html
Some country-TLD registrars do have this requirement, however. hmm. related question here then - webmaster@ addresses? assuming www.xxx.com and www.subsite.xxx.com, is it required / best practice to support a) just webmaster@xxx.com b) webmaster@ for each subsite c) some appropriate email address (referenced on the site) not in the same domain (if website domain != email domain)
Yo David! The answer is "b". Check out RFC 2142 "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND FUNCTIONS". "If a host is not configured to accept mail directly, but it implements a service for which this specification defines a mailbox name, that host must have an MX RR set (see [RFC974]) and the mail exchangers specified by this RR set must recognize the referenced host's domain name as "local" for the purpose of accepting mail bound for the defined mailbox name. Note that this is true even if the advertised domain name is not the same as the host's domain name; for example, if an NNTP server's host name is DATA.RAMONA.VIX.COM yet it advertises the domain name VIX.COM in its "Path:" headers, then mail must be deliverable to both <USENET@VIX.COM> and <USENET@DATA.RAMONA.VIX.COM>, even though these addresses might be delivered to different final destinations." RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 20340 Empire Blvd, Suite E-3, Bend, OR 97701 gem@rellim.com Tel:+1(541)382-8588 Fax: +1(541)382-8676 On Tue, 23 Oct 2001, David Howe wrote:
Some country-TLD registrars do have this requirement, however. hmm. related question here then - webmaster@ addresses? assuming www.xxx.com and www.subsite.xxx.com, is it required / best practice to support a) just webmaster@xxx.com b) webmaster@ for each subsite c) some appropriate email address (referenced on the site) not in the same domain (if website domain != email domain)
Yo David! On Mon, 22 Oct 2001, David Lesher wrote:
Every site should accept/respond to "postmaster" -- T/F?
RFC2821: " Any system that includes an SMTP server supporting mail relaying or delivery MUST support the reserved mailbox "postmaster" as a case- insensitive local name. This postmaster address is not strictly necessary if the server always returns 554 on connection opening (as described in section 3.1). The requirement to accept mail for postmaster implies that RCPT commands which specify a mailbox for postmaster at any of the domains for which the SMTP server provides mail service, as well as the special case of "RCPT TO:<Postmaster>" (with no domain specification), MUST be supported.'
Or is it "Every site running mail".... Or every box running mail?
I infer all the above from RFC2821 above.
IOW: Which of the following are required vice recommended vice best practives, etc.
a) postmaster@example.com Surely required. RFC2821 above.
b) postmaster@mail.example.com Required IFF mail.example.com has an SMTP daemon:
RFC1123: 'A host that supports a receiver-SMTP MUST support the reserved mailbox "Postmaster".'
c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com
Not required, but encouraged, RFC 2142: " For well known names that are not related to specific protocols, only the organization's top level domain name are required to be valid. For example, if an Internet service provider's domain name is COMPANY.COM, then the <ABUSE@COMPANY.COM> address must be valid and supported, even though the customers whose activity generates complaints use hosts with more specific domain names like SHELL1.COMPANY.COM. Note, however, that it is valid and encouraged to support mailbox names for sub-domains, as appropriate." Postmaster is related to a protocol (SMTP) so this does not exactly apply. Still, my logs show sending mail to sub-domains is a very common practice so I always MX all subdomains. I find this confirmed in RFC1123: "Be liberal in what you accept, and conservative in what you send"
and most important to me: where to I go to justify the decisions on same?
RFC822, RFC1123, RFC2142, RFC2821. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 20340 Empire Blvd, Suite E-3, Bend, OR 97701 gem@rellim.com Tel:+1(541)382-8588 Fax: +1(541)382-8676
wb8foz@nrk.com writes:
A query to help educate me. Feel free to flame away; the week is young.
Every site should accept/respond to "postmaster" -- T/F?
Or is it "Every site running mail".... Or every box running mail?
IOW: Which of the following are required vice recommended vice best practives, etc.
a) postmaster@example.com b) postmaster@mail.example.com c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com
and most important to me: where to I go to justify the decisions on same?
The Host Requirements RFC says that if you support "receiver SMTP", you must support the reserved mailbox "Postmaster". In my experience, interpreting that statement has been a pre-existing exercise for the readers for nearly a decade, with many results. In my humble opinion -- heavily dosed with Jon Postel's Robustness Principle -- that rule means that if SMTP mail succeeds to _any_ address for a specific right-hand side, then SMTP mail must also succeed to "postmaster" at that same right-hand side. So using your examples above, if I can send SMTP mail to foo@example.com, then I should be able to send SMTP mail to postmaster@example.com. I would hope that a real human being would be able to respond, but I realize it's unlikely. There may be other RFCs that cover this issue. Jim == Jim Duncan, Product Security Incident Manager, Cisco Systems, Inc. <http://www.cisco.com/warp/public/707/sec_incident_response.shtml> E-mail: <jnduncan@cisco.com> Phone(Direct/FAX): +1 919 392 6209
participants (7)
-
Brett Frankenberger -
David Howe -
David Lesher -
Gary E. Miller -
Jim Duncan -
Peter van Dijk -
Ryan O'Connell