La Poste starts enforcing SPF, DKIM and DMARC on all inbound email

The French postal service La Poste has announced that it now enforces stricter sender requirements on inbound email messages directed to its email service.

The changes are in effect starting 9 September 2025: if you send email from your domain to La Poste recipients, make sure you follow email best practices around SPF, DKIM and DMARC.

These new requirements follow the ones set by Gmail, Yahoo, Microsoft and Cloudflare over the past 2 years.

What’s changing

Simon Bressier, the person responsible for anti-abuse and deliverability at La Poste, announced on LinkedIn in August that starting September there would be new expectations around authentication of emails processed by the service.

Here’s the important bit, translated from French:

100% of emails that don’t present SPF, DKIM nor DMARC will be delivered to the junk folder in the best case.

More details were later published on SpamResource by Al Iverson:

Starting on Tuesday, September 9th at 9am (French time), laposte.net will enforce penalties for emails without any valid authentication (SPF, DKIM, or DMARC). Consequence: such emails will end up in the spambox at best, or be rejected.

Technical points:

• SPF and DKIM are also considered “none” if not aligned with the From (RFC5322.From).
• SPF: if the MailFrom (RFC5321) is not aligned with the Header From → SPF = none.
• DKIM: if the signed domain is not aligned with the Header From → DKIM = none.
• For routers using shared domains (MailFrom and/or DKIM), this will be treated as non-aligned, thus “none”.
• If multiple DKIM signatures exist, only one needs to be aligned.

This means that La Poste will start checking SPF and DKIM alignment, as DMARC dictates.

In the absence of any of these, La Poste will treat the authentication mechanism as not being present at all (“none”).

At least one of SPF alignment or DKIM alignment must pass in order to not be penalized. Note that having a valid SPF and DKIM configuration alone is not enough: you also need to ensure alignment.

What you should do

If you’re an email sender and want to prevent La Poste from rejecting your emails, you should make sure that:

• Your SPF configuration is valid (i.e. the IP addresses of your mail servers must be allowed by the SPF record of your domain).
• Your email messages are properly signed with a DKIM signature.

Additionally, it’s recommended that you enable the DMARC protocol to ensure successful delivery of email.

With DMARC, one of these two additional requirements must be satisfied:

• The SPF domain (Envelope From) must be aligned with the sender domain (From).
• The DKIM signature domain (d tag) must be aligned with the sender domain (From).

DMARC also gives you control on whether you want to enforce these checks or not, and most importantly lets you monitor your email flows to identify email authentication issues that could impact the delivery of the emails.