Rated 3 out of 5 stars

Works perfectly with other domains, where results match with online DKIM verification tools. However, with our own domain (which passes all DKIM online verification tools) it returns the error "Invalid (DKIM key is ill-formed)" on mails sent internally.

This review is for a previous version of the add-on (1.3.6). 

This is the wrong place to report bugs in the add-on.
Please e-mail me to dkim.verifier.addon@gmail.com or open a issue at https://github.com/lieser/dkim_verifier/issues.

Needed detail are at least your domain and used selector (to get the DKIM key). Best would be to provide an affected e-mail as a saved .eml file.