In the last eGroupWare version there is an additional patch which has to be applied before you can use FelaMiMail. The package can be found at eGroupWare's download page under the name:

eGroupWare-egw-pear-1.4.xxx-x.zip

You just have to unzip the file in the eGroupWare application root folder using cPanel -> File Manager -> Extract. Make sure that your FelaMiMail is configured to use the following details:

SMTP server: yourdomain.com
Port: 25
Use SMTP authentication. With the following login credentials:
Username: user@yourdomain.com
Password: the corresponding password