MichaelH I have the same problem, but a reinstall is no solution.
Yes, unfortunately I've had to find that out again now. After migrating several accounts to the new system with grommunio on Friday, I realized that the search in the web interface doesn't work for the other mail accounts :-(
The system is currently running productively (only for my family) but I am considering migrating back to Kopano...
Actually, I hope that a solution can be found in the next few days. Strangely enough, the search on my own account still works after the reinstallation.