When conducting a search within webmail, an error is returned stating:
UID SEARCH: Error in IMAP command UID SEARCH: Unknown argument
This behavior can result in corrupted Roundcube user preferences, specifically in the search_mods array, which stores the selected search options for each folder (To, From, Subject, etc.). Some folder names or other bad search options may be stored as search preferences for a specific folder, resulting in the error occurring only when searching that folder.
The suggestion is to clear the preferences which should return the normal functionality. This may be done with the following command:
Sqlite Roundcube Servers:
sqlite3 /home/$user/etc/$domain/$mail_user.rcube.db 'UPDATE users SET preferences = "" WHERE username = "email@example.com"'
MySQL Roundcube servers:
mysql roundcube -e "update roundcube.users set preferences = '' where username like 'firstname.lastname@example.org';"
*Please be sure to update the example path and user