Email Domains: DKIM
DKIM - DomainKeys Identified Mail
DKIM is a standard which has been created for the same reason as SPF: to prevent attackers from impersonating you as an email sender. It’s a way to additionally sign your emails to allow the recipient’s server to check if the sender was really you or not.
By setting DKIM on your DNS server, you’re adding an additional way to tell your receivers “yes, it’s really me who’s sending this message”.