On 7 Jul 2018, at 4.31, Infoomatic <infoomatic@gmx.at> wrote:

Hi,
I just upgraded from dovecot 2.2.19 to 2.3.2. "doveadm backup" worked fine in v 2.2.19, but now panics (user with shared folder):
/opt/dovecot/bin/doveadm backup -u testuser -1 sdbox:/tmp/testuser

Not sure why it panics, but at least your command line looks incorrect. 

please try: doveadm backup -u testuser sdbox:/tmp/testuser

your options are:

doveadm backup
doveadm sync
doveadm sync -1

https://wiki2.dovecot.org/Tools/Doveadm/Sync

Sami