Issue IONOS emails rejected with "dmarc: stderr: REJECT" although DMARC check is disabled

[TorbHo]

Server operating system version

Debian 11.11

Plesk version and microupdate number

18.0.75

Hello everyone,

we are currently experiencing an issue with incoming emails from IONOS.

Emails sent from IONOS are being rejected with the following error:

321886B24FBB: dmarc: stderr: REJECT
2026-02-10 09:18:54   err dmarc [3121468] 7BE936B20CD1: Wrong the essential DMARC policy parameters for 'domain.tld': 'Found DMARC record containd a bad v= value'

However, under Tools & Settings → Mail Server Settings, both DMARC and SPF checks are completely disabled.

Additionally, we are using an upstream spam filter that processes all incoming emails first and then forwards them to the Plesk server.

Given that DMARC and SPF verification are disabled in Plesk, we do not understand why emails are still being rejected due to DMARC with a "REJECT" result.

Has anyone experienced a similar issue or can explain why this is happening despite the checks being disabled?

Any help would be greatly appreciated.

Thank you in advance.

 

[TorbHo]

A short update regarding the previous issue with IONOS emails being rejected.

The problem is currently no longer occurring.

What I did:

1. I re-enabled SPF and DMARC under
   Tools & Settings → Mail Server Settings
2. Then I disabled both options again immediately.
3. After that, I ran: plesk repair mail -y

At the moment everything seems to be working correctly.
Maybe the settings were internally overwritten or not applied correctly during the last Plesk update to version 18.0.75?

 

[hschramm]

about the error at Ionos: Ionos had a bug in their dns records:

dmarc.ionos.de.         14746   IN      TXT     "v=DMARCv1; p=none;"

It seems they have fixed it.