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Re: [spf-discuss] PermError: Too many DNS lookups at Microsoft.com

2006-05-06 11:00:35

----- Original Message -----
From: "Scott Kitterman" <spf2(_at_)kitterman(_dot_)com>


With my validator, the MS SPF record is raising an error because
of too many DNS lookups.  Any chance someone who has a minute
(I don't today, I'm on a project deadline) could grind their
way through their records by hand and count them up?  I'm pretty
certain of my code in this area, but I'd like a double check....


What kind of DNS lookup limit do you have?

Anyway, this would be the lookup count assuming the entire SPF is processed:

lmap microsoft.com

  "v=spf1
   mx
   include:_spf-a.microsoft.com
   include:_spf-b.microsoft.com
   include:_spf-c.microsoft.com
   ~all"

Lookup #1 for mx produces + 3 includes:

  mail exchanger = maila.microsoft.com
  mail exchanger = mailb.microsoft.com
  mail exchanger = mailc.microsoft.com

This is 3 more lookups.

1 + 3 + 3

Sub total = 7


lmap _spf-a.microsoft.com

  "v=spf1
   ip4:213.199.128.139
   ip4:213.199.128.145
   ip4:207.46.50.72
   ip4:207.46.50.82
   a:delivery.pens.microsoft.com
   a:mh.microsoft.m0.net
   mx:microsoft.com
   ~all"

We got two A record looks plus another MX lookup on the same microsoft.com,
so we have:

2 + 4 = 6

Lookup sub total = 13
redundant sub total = 4

lmap _spf-b.microsoft.com

  "v=spf1
   a:delivery2.pens.microsoft.com
   a:delivery.smtp.microsoft.com
   a:smtp.msn.com
   mx:exchange.microsoft.com
   ip4:131.107.65.22
   ip4:131.107.65.131
   ip4:131.107.1.101
   ip4:131.107.1.102
   ip4:217.77.141.52
   ip4:217.77.141.59
   ~all"

We have 3 A lookups plus a MX lookup which produces:

    mail exchanger = maila.microsoft.com
    mail exchanger = mailb.microsoft.com
    mail exchanger = mail3.exchange.microsoft.com
    mail exchanger = mail4.exchange.microsoft.com

3 + 1 + 4  (2 redundant) = 8

Lookup sub total = 21
redundant sub total = 6

lmap _spf-c.microsoft.com

  "v=spf1
   ip4:131.107.1.18
   ip4:131.107.1.19
   ip4:131.107.1.20
   ~all"

No additional lookups:

If I did it right manually, the totals are:

Total DNS lookups: 21
Redundant Lookups: 6

Are you using the recursive limit of 20 for this?  I don't see a recursion
here, but there is redundancy.

--
Hector Santos, Santronics Software, Inc.
http://www.santronics.com





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