doveadm client not compatible with this server (mixed old and new binaries?)

[Kevin Golding]

On Wed, 23 Aug 2017 21:19:33 +0100, Pallissard, Matthew  
<dovecot at pallissard.net> wrote:

> I've ran into this after an upgrade of one of my instances.  For  
> whatever reason when I restarted the service there was still an old  
> process hanging around.
>
> Fully stopping the service, checking that there were no dovecot  
> processes running, then starting it up again resolved the issue.

Given I was confident that I always completely stop the service for any  
upgrades I confess I was somewhat skeptical about this, but it worked.

I did a full stop of the entire mail system on both machines before  
starting them again. Not restart, a stop command followed by a start  
command, and looking at the log files I'm no longer getting complaints  
about mixed binaries. I'm kicking myself for this one, but also grateful -  
thanks for that.