The scenario is:
- an IMAP server with little space (say 1GB)
- quite a few IMAP clients (say 2 phones, 1 tablet, 3 PCs) with an email client such as Thunderbird 38.3 or later
What I'd like to achieve is this:
- all PCs clients should keep a full copy (not just the header) of messages
- all PCs clients should save locally any message deleted remotely (i.e. move full message to a local folder before deleting it from its own IMAP folder, as a result of syncronization)
This way one could save space on IMAP server while keeping a local copy of all (full) messages on each PC (provided that PC clients are syncronized when an email is deleted from a non-PC client -- avoiding deletion from non-PC clients could be a workaround to ensure that local copies are complete).
I found some related questions that address similar scenarios (like this and this), but none gives a solution to this question.
I believe that this is quite a common need, so I hope that some email client guru, hopefully Thunderbird, come up with a solution.