Evade forced external mail archive. Was: Sync IMAP Mailboxes/Folders via ssh?

[Peter P. <pet...@fa...>]

Hi list,

reviving an older thread here, I am still looking for a solution to the
problem of my employer wanting to move all email in my account older than X
years from all folders and host it on a separate webservice[1], thus
making it inaccessible to me from isync/mutt/notmuch etc.
The employer is trying to save storage and server ressources this way
and this questionable move is unavoidable for me.

Denial Tamling has suggested using tools from the mblaze package to filter
mail older than a certain date, with Oswald pointing out a pitfall when
moving these messages, which I don't yet understand:

* Oswald Buddenhagen via isync-devel <isy...@li...> [2025-07-18 09:02]:
> On Thu, Jul 17, 2025 at 10:33:36PM +0200, Daniel Tameling wrote:
> >  mv $(mlist ./INBOX | mpick -t 'from =~ "@github"') ./github/cur
> > 
> this will preserve the ,U=nnn infixes of the files, which is a very bad
> idea.

Is there a correct way to move all mail from all folders older than X to
some other folder?

I am wondering if mblaze/mlist is nevertheless the best way I can
anticipate the forced archival.

If I would manage to hereby extract all old email from all far-side
folders I would then need to store it to a near-side folder that is not
synced back to the far side. How could I nevertheless keep that
near-side folder in sync across multiple computers? 

Is there any other way to work around this imminent problem?

Thank you so much!
best, Peter

[1] https://www.opentext.com/products/retain-unified-archiving