> Hi list, > > I saw this in my logs: > > Apr 29 14:58:08 mx postfix/smtpd[4880]: connect from > xxx.yyy.zzz[xxx.yyy.zzz.xxx] > Apr 29 14:58:09 mx postfix/smtpd[4880]: warning: valid_hostname: empty > hostname > Apr 29 14:58:09 mx postfix/smtpd[4880]: warning: malformed domain name > in resource data of MX record for somedomain.com:
There is no Internet RFC that says that an empty hostname is valid. Postfix was not built by experimentation of "what works". Instead, Postfix was built by looking at official email standards. Then, I added hacks and workarounds for systems that don't play by the rules. > Apr 29 14:58:09 mx postfix/smtpd[4880]: NOQUEUE: reject: RCPT from > xxx.yyy.zzz[xxx.yyy.zzz.xxx]: 450 4.1.8 <i...@somedomain.com>: Sender > address rejected: Malformed DNS server reply; from=<i...@somedomain.com> > to=<u...@example.com> proto=ESMTP helo=<xxx.yyy.zzz> > Apr 29 14:58:09 mx postfix/smtpd[4880]: disconnect from > fxxx.yyy.zzz[xxx.yyy.zzz.xxx] > > And: > > $ host somedomain.com > somedomain.com has address yyy.zzz.xxx.yyy > somedomain.com mail is handled by 0 . > > This looks like a Null MX record: > http://tools.ietf.org/html/draft-delany-nullmx-00 > > If the domain owner declares that this domain never sends or recieves > email, then shouldn't postfix reject the above message with a permanent > error? Anyone can post a draft. That does not mean that they change the rules of the Internet. The SMTP RFC says that the MX record specifies a hostname, and there is no RFC that says an empty string is a valid hostname. The warning message is an example of a workaround hack that I put in for systems that don't supply valid hostnames in their MX records. Wietse
