TLDR: after enabling Apple Mail Plug-in, DT3 must also be restarted, to facilitate importing an intact mailbox hierarchy
I am starting to archive my old email in Apple Mail to DT3. I used the “import” panel in the left sidebar and used “archive mailbox”. One important aspect is to preserve the mailbox structure. Initially, this did not work; while the mails where imported, the mailbox structure was flattened. I realized that even though I had installed the DT Apple Mail plug-in, I had failed to enable it manually in Apple Mail (preference > general > manage plug-ins). I enabled it and Mail restarted. Everything looked good. Yet, the archived mailbox structure was still flat.
Solution: turns out that DT3 must also be restarted. After doing that, everything worked as promised.
When I was still running Ventura and could use the Apple Mail plug-in, importing with the Archive Mailbox function in the Emails section of the View>Import sidebar worked as expected. Now that I’ve had to upgrade to Sequoia I find that the structure of Apple Mail is ignored - the structure of nested mailboxes has been flattened out to an alphabetic list of all mailboxes. Is this because it’s working without the plug-in? The structure is flattened in the sidebar, and it imports flattened as well, whereas previously it retained the structure of mailboxes and sub-mailboxes. What to do?
@BLUEFROG Any idea of how long whatever improvements might take? It has been relatively easy to update the mailbox archive(s). Now it seems to be ridiculously labour- intensive. Unless there’s a better way?