1.2 Illegal MX record for recipient host domain part looked up is shown
here
??? If any of the IP addresses returned in the MX list begin with 127.0 (the loopback
interface) or 10. (a nonrouting address) or 0. (a broadcast address), that address
is considered bad and the following SMTP error is returned to the client and the
connection is refused:
550 5.1.2 Invalid MX record for recipient host domain part looked up is shown
here
This is the Title of the Book, eMatter Edition
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292 | Chapter 7: How to Handle Spam
The FEATURE(badmx) uses the bestmx database map (?§23.7.3 on page 902); the regex
database map (?§23.7.20 on page 932); and the dns database map (?§23.7.6 on page
905). You may use this FEATURE(badmx) only if sendmail was built withsupport for all
three database-map types.
7.6.2 FEATURE(block_bad_helo)??”V8.14 and Later
The HELO and EHLO client SMTP commands are eachformed by a command followed
by a hostname:
HELO client.host.domain
EHLO client.host.domain
According to RFC2821, the hostname provided by the client (following the HELO or
EHLO SMTP) must be:
??? The canonical hostname of the sending client machine. That is, a host with a
domain part. For example, the name ???foo??? is bad because it lacks a domain. The
name ???.com??? is bad because it lacks a host part.
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