Boy it was a long time ago that I did anything with gpg. Here is how to generate and sign keys.
[WayBack] gpg creation and sign Gino’s Key ($1785651) · Snippets · GitLab
And here to check your email confguration:
[WayBack] Home – dmarcian Founded in 2012 by the primary author of the DMARC specification, dmarcian is dedicated to upgrading the entire world’s email by making DMARC accessible to all. dmarcian brings together thousands of senders, vendors, and operators in a common effort to build DMARC into the email ecosystem.
–jeroen