One longtime feature of the macOS Mail App is Previous Recipients. The Previous Recipients feature works like this. You create a new Email. When you start to type the person’s email address in the “To” box, the Mail App drops a list of possible recipients from previous emails. Occasionally, this Previous Recipients list can have outdated emails in it. If you would like to clean up that list by removing some of these outdated emails, then this is how you do it.
You can remove outdate recipients in the Previous Recipients window.
Once in this area, you will see a list of Previous Recipients.
I blocked out the names for Privacy reasons. All you have to do is select the recipient you wish to delete and click on “Remove From List”.
The Email address is removed instantly, no warning message. It is not a bad idea to scroll through this list and remove other emails that are no longer valid. This will save you time when you address emails in the future.
Typing peoples Email addresses is a real drag. The Mail Previous Recipients list is a real time saver.