I have searched but not found the answer to this particular question.
I have two Macs, A and B. Both have only IMAP Mail accounts so have all the same email.
On Mac A, I have just successfully imported all my email using the “Archive email” option in the Importer tab. This has all gone into a dedicated new database which is sync’d to Mac B with Bonjour.
Running “Archive Mail” again on Mac A imports only the latest mail. All good so far.
The question is can I use “Archive Mail” on Mac B to update the database with the latest mail, or will Mac B see all existing emails as different because they were imported on Mac A? Hence try to import the whole 100k emails again, as duplicates.