Rated 2 out of 5 stars

All emails are apparently invalid and have been modified. Even those that come from known and trusted security focused services.

EDIT: Reading your Wiki link indicates that your extension doesn't work with one of a largest email providers - Microsoft.

It looks like a well known issue to you and yet there is no mention of it on the extension's Add-Ons page. I think it would it be appropriate to add it.

I'm not reporting a problem, I'm reviewing the extension. As it stands, it doesn't work and this review is a signal to others that there are issues with it.

Αυτή η αξιολόγηση γράφτηκε για παλιότερη έκδοση του πρόσθετου (5.3.1). 

This is probably a problem of your e-mail provider, who modifies incoming e-mails. See https://github.com/lieser/dkim_verifier/wiki/FAQ#all-or-almost-all-e-mails-with-dkim-signature-are-failing-with-the-same-error for more information.

Next time please don't use the reviews to report problems. Use https://github.com/lieser/dkim_verifier/issues or write me an E-Mail (in English or German).