Check if upgrading kopano-server to 8.5.7 and up will succeed

Open a MySQL console
Run the following command:
```
mysql> SELECT MAX(id) from names;
```
If the printed result is 31485 or higher you will have to clean the database using the kopano-dbadm utility.
Next, run the second command:
```
mysql> select namestring, count(*) as c from names group by guid,nameid,namestring having c>=2;
```
This checks the table for duplicates, printing any it finds.
If this returns anything you have duplicate entries in your "names" table that can be cleaned by kopano-dbadm utility.
If the table contains less than 31485 entries and no duplicates, you can upgrade to 8.5.7 without running into the K-1216 error.