[Dovecot] doveadm altmove to gzipped-mdbox

[Claus]

Hi,

im wondering if it's possible to store old messages in a compressed 
mdbox on alternate storage.
The main storage is uncompressed mdbox.

I tried something like: doveadm -Dv -o "plugin/zlib_save=gz" altmove -u 
testuser sentbefore 8d

Could someone tell me if it's possible and give me a hint how this can 
be done?

I tried this with dovecot-2.2

Claus