E-mail NDR: #5.1.1 SMTP; 550 Rejecting for Sender Policy Framework (SPF too many lookups)


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One of our clients was having issues sending an e-mail to one of our regional ISP’s e-mail servers.

  • Remote Server returned ‘<inbound.server.com #5.1.1 SMTP; 550 Rejecting for Sender Policy Framework>’

    • SPF too many lookups

There was no further information. The specifics came from a very helpful mail technician at the ISP.

So, we started to dig around and came up with the following:

A ticket went through Third Tier’s Help Desk this week that was based on this problem with Dave Shakelford pointing to the following blog post:

So, what does all of this mean?

It means that we need to make sure all of our clients that send mail via an ISP SMTP server, third party sanitation and continuity service, or mail hosting service need to have a correct SPF record in place.

It also means that edge sanitation is starting to catch up with the SPF revisions in RFC 7208 as per the OpenSPF site.

As the JangoMail blog post makes clear, we may have to jump through a few hoops to get it right, but get it right we must as our client’s mail is critical to their business.

Philip Elder
Microsoft Cluster MVP
MPECS Inc.
Co-Author: SBS 2008 Blueprint Book

Original Post Here: MPECS Inc. Blog: E-mail NDR: #5.1.1 SMTP; 550 Rejecting for Sender Policy Framework (SPF too many lookups)

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