The error handling check against fts_backend_xapian_lookup was wrong which resulted in returning always an error.
fts_backend_xapian_lookup_multi did not pass the collected results on to the dovecot FTS backend. Thus dovecot virual folder search did not work and produced the following IMAP error:
xx NO [SERVERBUG] Internal error occurred. Refer to server log for more information
The error handling check against
fts_backend_xapian_lookup
was wrong which resulted in returning always an error.fts_backend_xapian_lookup_multi
did not pass the collected results on to the dovecot FTS backend. Thus dovecot virual folder search did not work and produced the following IMAP error:xx NO [SERVERBUG] Internal error occurred. Refer to server log for more information