antispam plugin pipe backend error when moving multiple emails

Hi,

I've got some trouble with the dovecot antispam plugin and the pipe backend.

I'm using dovecot 2.2.18 with maildirs and zlib compression enabled.

When moving 2 or more emails at once from the Junk folder to another one, I always have the following error : "Failed to copy to temporary file"

In the server logs :

imap(vvv@vvv.vvv): Error: read(zlib(/data/Maildir/.test/tmp/1446974366.M123890P936.vvv)) failed: Cached message size smaller than expected (13553 < 13562, box=test, UID=0)

The same operation with one email at a time, on the same emails, works as expected.

Stéphane