Postmaster (computing)
If you are looking for other meanings of this word, see Postmaster (disambiguation)
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.
Since 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
For example, most error emails automatically generated by mail servers MTAs 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.
Quoting from the RFC itself: "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.
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.
rfc-ignorant.org: Lists domains where the postmaster@ address is not supported