Horde webmail displays the alike warnings instead of the messages titles in the interface:
The message: "<message subject>" (123123123 Bytes) exceeds the fetch size limit
Find out what PHP configuration file Horde uses by accessing the following URL: http://webmail.domain.com/test.php?mode=phpinfo&url=%2Ftest.php
'domain.com' should be substituted with your actual domain name.
Correct Horde configuration files and increase the following limit (by default it is 4MB):
[root@ppa2 ~]# cat /etc/psa-webmail/horde/imp/conf.php|grep fetchmail|grep size $conf['fetchmail']['size_limit'] = 4000000;
Increase the following PHP settings in the configuration file that was determined on step 1:
# grep -E "upload_max_filesize|post_max_size" /etc/php.ini upload_max_filesize = 64M post_max_size = 128M