spf-discuss
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the "implicit-MX" rule and a proposed BCP

2004-02-13 15:20:55
On Thu, Feb 12, 2004 at 11:37:34PM -0800, Greg Connor wrote:
| 
| Unfortunately this means all A records also need SPF records. I wonder if 
| something like this could give the proper result:
| 
| Interesting.  Anyway it's probably safer to SPF anything that has either MX 
| or A including *

Our MX server boggle recently got this error:

  when we tried to send mail to holborn-ed(_at_)real-life(_dot_)tm, the 
receiving
  host mailgate.real-life.tm[195.11.8.2] said: 550 Sorry, the domain
  "boggle.pobox.com" has no MX records. (in reply to RCPT TO command)

so mailgate.real-life.tm has an antispam rule that refuses all sender
domains with no MX records.  In a world where the implicit-MX rule was
deprecated, that behaviour would be the norm.

So what did we do?  We added MX records to all our mail servers.

I feel a BCP coming on that deprecates the implicit MX rule and
recommends that all envelope sender domains should have an MX record in
addition to an A record.  And an SPF record, too, obviously.

If that became the custom, then we wouldn't have to add SPF records for
A-only subdomains.