I did not solve my question I clicked the wrong place. Any way to undo the "This solved my quesion"?
No - I am afraid you cannot undo it.
As I may have indicated you should try to simplify your email by, perhaps:
- emptying Trash more often
- using either entirely POP or entirely IMAP
- having the same messages and accounts on both computers
I know more than most about POP but not so much about IMAP but here goes:
Most email servers are IMAP with a very efficient POP facility. Some email servers, such as First Class and IOL, do more than the specifications.
POP only downloads from the server's Inbox so if you use web or IMAP to access the same account you should be aware that messages moved to other folders before being downloaded by POP will not be available to POP clients unless they are returned to the server's inbox.
IMAP synchronizes folder contents between server and client so other IMAP clients will see the same folder structure and folder contents. I think this should also be so for trash. 'On My Mac' folders are local only and are not synchronized.
Apple Mail keeps a record of downloaded emails in MessageUidsAlreadyDownloaded. I only use POP and can delete this file and get all my emails downloaded again from the server. You can set the number of days that POP accounts retain messages on the server. Apple Mail preferences only provides a limited number of times to retain messages on the server but the plist can be edited to set any number of days. I set mine to 122 days - 4 months.
A POP server stores messages in a single mbox file. If you own the server or have direct access to it you can move this file to a POP client and have instant access to all stored messages. I did this once with thousands of emails - much faster than downloading them one at a time.
I have noticed that some POP servers do not instantly remove messages they are instructed to delete but it gets resolved eventually.
I have already told you how to make the Mail accounts on both computers exactly the same. I have also given you a link to a method for keeping POP accounts synchronized in the future.
I would be surprised if the the following does not resolved your problem:
- Edit POP account preferences to delete from server after a specified time
- Move IMAP account unwanted emails to its Trash folder - not the 'On My Mac' Trash - this is what Gmail says: https://support.google.com/mail/answer/78755
