On 13 Dec 2015, at 19:56, Alexander Moisseev <moiseev@mezonplus.ru> wrote:

doveadm expunge -u user@example.com MAILBOX Trash ALL

Fatal: expunge: To avoid accidents, each branch in search query must contain something else besides MAILBOX (e.g. just add "all" if you want everything)

Fixed: https://github.com/dovecot/core/commit/6971937a6f3e93844dbd43bdbe903628e21a9...

Also as workaround you can use 1:* instead of ALL.