Rated 4 out of 5 stars

Does not work on this beta version.

This review is for a previous version of the add-on (1.7.0). 

Please don't use the reviews to report problems. Use https://github.com/lieser/dkim_verifier/issues or write me an E-Mail.
See also https://addons.mozilla.org/en-US/review_guide

Have you tried the last pre-release from https://github.com/lieser/dkim_verifier/releases?