[Mimedefang] Revisit: Filtering on HELO
jebright at esisnet.com
Mon Mar 19 10:05:46 EST 2007
On Sun, 18 Mar 2007 09:47:38 -0400, Kevin A. McGrail wrote
> No, I don't believe it would because this is in the definition of
> the FQDN not the IP Literal.
> Unfortunately, I don't believe the FQDN definition changes my
> original statement.
Let me say, my HELO/EHLO filering is pretty much identicle to KAMs, and I have
had few if any complaints running it for several years now.
Here is the section of the RFC sepcific to domains that I believe resolved
most if this argument:
Only resolvable, fully-qualified, domain names (FQDNs) are permitted
when domain names are used in SMTP. In other words, names that can
be resolved to MX RRs or A RRs (as discussed in section 5) are
permitted, as are CNAME RRs whose targets can be resolved, in turn,
to MX or A RRs. Local nicknames or unqualified names MUST NOT be
used. There are two exceptions to the rule requiring FQDNs:
- The domain name given in the EHLO command MUST BE either a primary
host name (a domain name that resolves to an A RR) or, if the host
has no name, an address literal as described in section 220.127.116.11.
- The reserved mailbox name "postmaster" may be used in a RCPT
command without domain qualification (see section 18.104.22.168) and
MUST be accepted if so used.
This pretty much spells out exactly what is required when domain naames are
used within SMTP communications.
James R. Ebright
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