By default, PHP limits uploaded files' size to 2 MB. This limit applies to all PHP applications including Webmail.

To change this log onto the server via SSH and edit the following options in the /etc/php.ini file.

(If you have changed the default php.ini file for a site then that is the one you will need to edit)

upload_max_filesize = 32M

post_max_size = 32M

Once you have made these changes, save the file and reload (not restart) the http service.

CentOS - `/etc/init.d/httpd reload`

Debian/Ubuntu - `/etc/init.d/apache2 reload`