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In computers and technology, a postmaster is the administrator of a mail server. Nearly every domain should have the e-mail address postmaster@example.com where errors in e-mail processing are directed. Error e-mails automatically generated by mail servers' MTAs usually appear to have been sent to the postmaster address.

Every domain that supports the SMTP protocol for electronic mail is required by RFC 5321 and, as early as 1982, by RFC 822, to have the postmaster address. The rfc-ignorant.org website used to maintain a list of domains that do not comply with the RFC based on this requirement, but was shut down in November 2012. The website RFC² Realtime List expanded to include rfc-ignorant's lists after they shut down.

Quoting from the RFC:

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).^[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.

SMTP systems are expected to make every reasonable effort to accept mail directed to Postmaster from any other system on the Internet. In extreme cases (such as to contain a denial of service attack or other breach of security) an SMTP server may block mail directed to Postmaster. However, such arrangements SHOULD be narrowly tailored so as to avoid blocking messages which are not part of such attacks.

Since most domains have a postmaster address, it is commonly targeted by spamming operations. Even if not directly spammed, a postmaster address may be sent bounced spam from other servers that mistakenly trust fake return-paths commonly used in spam.

References

^ In the case of a connection-opening response, 554 means "No SMTP service here", and may contain explanatory information.

External links

RFC 5321: The SMTP Protocol

This computing article is a stub. You can help Wikipedia by expanding it.

[1] In the case of a connection-opening response, 554 means "No SMTP service here", and may contain explanatory information.

[1]

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+{{one source|date=April 2014}}
-''If you are looking for other meanings of this word, see [[Postmaster (disambiguation)]]''
+In [[computers]] and [[technology]], a '''postmaster''' is the administrator of a [[mail server]]. Nearly every domain should have the [[e-mail address]] postmaster@example.com where errors in [[electronic mail|e-mail]] processing are directed. Error e-mails automatically generated by mail servers' [[Mail transfer agent|MTA]]s usually appear to have been sent to the postmaster address.
+Every domain that supports the [[SMTP]] protocol for electronic mail is required by {{IETF RFC|5321|link=no}} and, as early as 1982, by {{IETF RFC|822|link=no}}, to have the postmaster address. The rfc-ignorant.org website used to maintain a list of domains that do not comply with the RFC based on this requirement, but was shut down in November 2012.  The website [http://rfc-clueless.org/ RFC<sup>2</sup> Realtime List] expanded to include rfc-ignorant's lists after they shut down.
-In [[Computers]] and [[Technology]], '''Postmaster''' is a term, used to identify the administrator of a [[mail server]]. Nearly every domain will have the [[email address]] postmaster@thedomain.com where errors in email processing are directed. This is required of any domain that supports the [[SMTP]] protocol, and since most domains will support email, they must provide this address.
+Quoting from the RFC:
-Since [[spammers|Spam (email)]] are aware that most domains have a postmaster address, it is a favorite target of the spammer community. Even if not directly spammed, because of spoof email return addresses in spam, the postmaster address will be sent bounced spam if a spammer is using your email address as a fake return address. For example, if a spammer tries sending email to someone@somedomain.com, and it bounces (due to any number of reasons) and the fake return address is you@yourdomain.com, then an automatic email will be generated to postmaster@yourdomain.com informing
+<blockquote>
-For example, most error emails automatically generated by mail servers [[MTA]]s usually appear to have been sent to the postmaster address. Each domain is required to have the postmaster address according to RFC 2821. The rfc-ignorant.org website maintains a list of domains that do not meet this requirement of RFC 2821. This doesn't necessarily make it a bad domain, just one that doesn't follow this particular protocol.
+Any system that includes an SMTP server supporting mail relaying or delivery MUST support the reserved mailbox "postmaster" as a [[case sensitivity|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).<ref>In the case of a connection-opening response, 554 means "No SMTP service here", and may contain explanatory information.</ref>  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.
+</blockquote>
+<blockquote>
-Quoting from the RFC itself:
+SMTP systems are expected to make every reasonable effort to accept mail directed to Postmaster from any other system on the Internet. In extreme cases (such as to contain a denial of service attack or other breach of security) an SMTP server may block mail directed to Postmaster.  However, such arrangements SHOULD be narrowly tailored so as to avoid blocking messages which are not part of such attacks.
-"Any system that includes an SMTP server supporting mail relaying or
+</blockquote>
-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.
+Since most domains have a postmaster address, it is commonly targeted by [[e-mail spam|spamming]] operations. Even if not directly spammed, a postmaster address may be sent [[bounce message|bounced]] spam from other servers that mistakenly trust fake [[return-path]]s commonly used in spam. <!--For example, if a spammer tries sending email to someone@somedomain.com, and it bounces (due to any number of reasons) and the fake return address is you@yourdomain.com, then an automatic email will be generated to postmaster@yourdomain.com informing --><!-- this needs to be completed -->
-SMTP systems are expected to make every reasonable effort to accept
-mail directed to Postmaster from any other system on the Internet.
-In extreme cases --such as to contain a denial of service attack or
-other breach of security-- an SMTP server may block mail directed to
-Postmaster.  However, such arrangements SHOULD be narrowly tailored
-so as to avoid blocking messages which are not part of such attacks."
-close quote.
+==References==
-[http://www.rfc-ignorant.org/ rfc-ignorant.org: Lists domains where the postmaster@ address is not supported]
+<references/>
+==External links==
+* {{IETF RFC|5321|link=no}}: The SMTP Protocol
+[[Category:Email]]
-{{stub}}
+{{Compu-stub}}