Validation error with senders email

I am not the first with this problem, but I’d appreciate having a solution to avoid “Senders email address does not belong to the site domain”.

My email domain matches the WordPress domain. Just like [email protected] for https://example.com. Still, I get “Senders email address does not belong to the site domain”.

I have disabled the validator now (https://contactform7.com/configuration-validator-faq/#can-i-disable-it). I hope only temporarily.

Thanks for your help!