Automatically remove old e-mail messages with Thunderbird (from IMAP server only, not locally)

Question

Given

• IMAP E-Mail provider/server with storage quota
• Thunderbird e-mail client

I'd like to automatically remove the oldest messages from the server only (and keep them locally).

But Thunderbird only seems to allow removing old messages from both, the server and local copies. The following can be found in Account Settings > Synchronisation and Storage:

To recover disc space, old messages can be permanently deleted, both local copies and originals on the remote server.

The same applies to Folder Properties > Retention Policy:

This post from 2010 suggests:

Set up a message filtersto move messages more than NN days old from the IMAP folders to folders under Local Folders created to receive them. Then right click on the name of the IMAP folder and select "Properties" from the context menu. Click on the "Retention Policy" tab and set the policy on that folder to delete messages more than NN days old.

but I have a feeling that what I would like to achieve would be a normal use case and as such there may be another solution. On the other hand, the archiving function apparently cannot be automated either while it would have to work in conjunction with the automatic deletion.

What am I missing?

This answer suggests using local folders which the Mozilla help / support search does not seem to be able find anything about (see http://kb.mozillazine.org/Local_Folders) and which I presume might cause complications when using several accounts.