This error can be seen in your mail client and is often caused by Courier. If you are the system administrator of the mail server, simply install libgamin as follows:
If you are root:
apt-get install gamin
If not:
sudo apt-get install gamin
Restart all of your courier services as follows (requires you to be using bash shell):
If you are root:
find /etc/init.d/ | grep courier | while read line; do $line restart; done
If not:
find /etc/init.d/ | grep courier | while read line; do sudo $line restart; done