Debian Jessie comes with systemd so you really should not use initscript anymore but 
switch to systemd for starting dovecot. There is systemd service description file available 
for you in case your vendor does not provide it in the package:

https://github.com/dovecot/core/blob/master/dovecot.service.in

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> i use ./configure with
> --with-systemdsystemunitdir=/etc/systemd/system/ and that installs the
> systemd.service and socket

That's what I missed, thank you a lot. And service seems to handle
correctly restarts 

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