HowTo: Apple Mail- Export/Import Mailbox (2020)

Apple allows you to transfer all of your files to another Mac via an app called Migration Assistant. However you may just want to either clean out your Mail and start with a clean copy or transfer it to a new clean Mac and leave behind any problems. This is easily done by Exporting your mailbox from the old copy of Mail then Importing it into the new Mail app.

Here is how...