Date: Mon, 25 Feb 2002 15:08:48 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: "Jeremy C. Reed" <reed@reedmedia.net> Cc: FreeBSD Chat <chat@freebsd.org> Subject: Re: blocked mail Message-ID: <3C7AC400.B8F3E9FC@mindspring.com> References: <Pine.LNX.4.43.0202251413410.25937-100000@pilchuck.reedmedia.net>
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"Jeremy C. Reed" wrote: > On Mon, 25 Feb 2002, Matthew D. Fuller wrote: > > On Mon, Feb 25, 2002 at 12:08:59PM -0800 I heard the voice of > > Jeremy C. Reed, and lo! it spake thus: > > > If you don't have an MX record then it tries the A record (which is the IP > > > for the hostname). > > > > Not if your mailer follows the RFC's strictly. > > Where is this documented? > > Section 5 of RFC 2821 says: > > ... > If no MX records are found, but an A RR is found, the A RR is treated as > if it was associated with an implicit MX RR, with a preference of 0, > pointing to that host. If one or more MX RRs are found for a given > name, SMTP systems MUST NOT utilize any A RRs associated with that > name unless they are located using the MX RRs; the "implicit MX" rule > above applies only if there are no MX records present. If MX records > are present, but none of them are usable, this situation MUST be > reported as an error. The DNS RFC's on SRV records. BTW, many of us really, really objected to the CNAME part of section 5, there, since it means that you have a large reverse list to look at for IP address matching, if you try to insist that a peer SMTP reverse resolve to an A that forward resolves to the same IP. In addition, the MX requirement is often that the sending host be in the MX list for the "MAIL FROM <user@domain>" domain part, or the mail will be refused as a suspicious relay. Enabling SPAM with an RFC doesn't mean that people will run out and implement the change. Probably he meant the pre-RFC2821 standard, which is what most mail servers on the In ternet still conform to today, and probably will for a very long time (may Jon Postel's name live forever). FWIW: RFC-821 is a standard, while RFC-2821 is only a proposed standard. 8-). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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