Webmail session times out while typing message

The session have a max amount of time before they expire.  Browing in /webmail will refresh this time, but when you're typing a message, if you take too long, the session will expire.  This will end up giving you a login page instead of sending the message causing you to lose the message.  To increase the time allowed, edit:

/var/www/html/webmail/inc/config.security.php

and set:

########################################################################
# Session timeout for inactivity
########################################################################

$idle_timeout = 10; //minutes

to a higher value.