syncing mailboxes with dsync after switchover

[Timo Sirainen]

> On 16 Mar 2016, at 02:04, Sergey Schwartz <sergey.schwartz at bgoperator.com> wrote:
> 
> Gentlemen,
> 
> I guess my mistake was to use *-R* option, that works similar to *-1* and your messages can get lost.
> 
> -R     Do  a  reverse  sync.  Normally, messages would be pushed from the local system to the destination (remote). This option reverses the flow, and will
>              instead pull messages from the remote to the local storage.
> 
> doesn't say clearly that it works like a backup mode and data can be lost

Oh, that really shouldn't have been even allowed. Fixed: 
https://github.com/dovecot/core/commit/7a3b52b8f9c6261ea912d9c96b20d815f782be5b