Musings from a small IPP

Today a customer wrote to ask for help getting mail from a company — let’s call it X — hat was suddenly not getting through.

X has 4 SPF rrcords

• v=spf1 mx include:isp1 -all
• v=spf1 mx include:isp2 -all
• v=spf1 mx include:isp3 -all
• v=spf1 mx include:isp4 -all

So depending on which of these four records is randomly received first, one of their supporting ISPs is authorized to forward X’s outbound email, — and — the other three ISPs are not authorized.   Actually X also had a syntax error in one of their 4 records which seriously did not help.

The SPF record X should have is of course:

• v=spf1 mx include:isp1 include:isp2 include:isp3 include:isp4 -all