July 09, 2026
What is a DKIM selector (and why there are several)
The DKIM selector points a receiver to the right public key. What it is, where it appears in a signature, and why one domain often carries several.
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July 08, 2026
SPF for Microsoft 365 and Google Workspace: the setup that works
SPF for Microsoft 365 and Google Workspace, separately or together, without busting the 10-lookup limit. The right includes, traps, third parties.
Read →July 07, 2026
SPF PermError: what it means and how to fix it
An SPF PermError makes the record impossible to evaluate, so it is ignored. Causes: 10 lookups, syntax, void lookups, duplicates, and the fixes.
Read →July 06, 2026
How to check an SPF record (and what to actually look at)
Checking an SPF record is not confirming it exists: it means reading its syntax, lookup count, qualifier and alignment. The complete step-by-step guide.
Read →July 05, 2026
SPF -all or ~all: what's the difference, and which to choose
SPF -all or ~all: what the terminal mechanism tells receivers, how ?all and +all differ, the interaction with DMARC, and which one to publish.
Read →July 04, 2026
What is SPF flattening (and when to actually use it)
SPF flattening swaps includes for the IPs they resolve to, to get back under 10 lookups. How it works, the maintenance debt, and the alternatives.
Read →July 03, 2026
SPF 'too many DNS lookups': understanding and fixing the 10-lookup limit
The PermError “too many DNS lookups” breaks an SPF record past 10 resolutions. Why the limit exists, what counts toward it, how to get back under.
Read →July 02, 2026
Is migrating to DMARCbis necessary? The no-stress checklist
DMARCbis replaces RFC 7489 but stays backward-compatible. What should change in the DMARC record, what must not, in which order, and how to verify.
Read →July 01, 2026
The end of the pct tag: DMARCbis's t= testing mode
DMARCbis drops the pct tag for t=, a binary testing mode. Why pct disappeared, how t=y behaves, and how to roll DMARC out gradually without it.
Read →June 30, 2026
DMARCbis's DNS Tree Walk: the end of the Public Suffix List
DMARCbis replaces the Public Suffix List with the DNS Tree Walk to find the organizational domain. How it works, why it is more robust, what changes.
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