It is not possible to access Horde webmail or open specific menus in webmail with one of the following error messages:
SQLSTATE[42S02]: Base table or view not found: 1146 Table 'horde.horde_prefs' doesn't exist
Server error when querying database.
A fatal error has occurred Could not instantiate PDO. PDOException: SQLSTATE[HY000]  Unknown database 'horde'
In Plesk, it is not possible to remove/rename an email account or rename a domain with the error message:
DB query failed: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'horde.TABLE_NAME' doesn't exist, query was:
The database of Horde webmail is missing or corrupted.
Note: If Horde webmail is not required on the server and another webmail is being used server-wide (Roundcube/MailEnable), remove the Horde component from the server.