I found a way to maybe solve this bouncing errors and that would be by turning on the feature ”Hide ’From’ Addresses” in the list software.
When this option is selected, the 'From' address of the posted messages is modified, so it contains the list email address instead of the message author email address.Â
If the original 'From' address contained a comment (a real name of the message author), it is preserved. The 'From' addresses in the message archives, digests, and indexes are converted, too.Â
The bouncing is not the media-motion list servers fault, it’s Yahoo who implemented the DMARC policy, so when a Yahoo subscriber on the list posts to the list, all users from Yahoo, Verizon and Gmail get bounced.
A solution to stopping the bounce messages to be sent out is to set the server to never unsubscribe because of bounced mail, but then all Yahoo, Verizon and Gmail subscribers would stop getting mail from this list.