DKIM settings/DMARC signatures

[reception]

Having issues contacting @icloud/@mac addresses - apple support says that they are not able to validate our DKIM settings, that it may be an issue with the DMARC signatures. How can I fix this (please be specific).

Thank you

[SKaero]

I can't give specifics on how to setup DMARC since it relies on on DKIM and to a lesser extent SPF and parts of that need to be setup on the mail server and other in DNS reocrds. No configuration needs to be changed in Roundcube. Here is a overview of all the parts and what they do: https://www.cloudflare.com/learning/email-security/dmarc-dkim-spf/