Horde is not showing inbox messages!!!

Following steps will solve the issue:

1) Take the backup of horde database (/hordebackup.sql).

mysqldump -uadmin -p'cat /etc/psa/.psa.shadow' horde > horde_backup.sql

2) Run the below mysql queries for horde database.

mysql> select * from horde_prefs where pref_uid='abc@xyz.com' and pref_name='sortpref';

mysql> delete from horde_prefs where pref_uid='abc@xyz.com' and pref_name='sortpref';

Issue fixed :)