Webuzo - Single User Control Panel allows users to create email account for their domains by deploying the Email Server (Exim + Dovecot) by a click of a button. Exim and Dovecot can be installed from the Webuzo Enduser Panel >> Apps >> Utilities Category. If at all you encounter a "550 relay not permitted" error in Webuzo while trying to send email then the following guide will help you fix it. Emails Accounts created using Webuzo are often configured to the desktop environments using tools like Outlook, Mozilla Thunderbird, etc. Note : The Fix is applicable only for Webuzo installed on CentOS 6.x as it install Exim 7.2 which handles the fix. One of the Quick Step is to verify if the Email Server is up and running on Webuzo and a Restart is recommended if you are unable to send/receive emails. Quick Guide : http://webuzo.com/wiki/Restart_services The following changes are required so as to get away with the "550 relay not permitted": 1) Dovecot Configuration /etc/dovecot/conf.d/10-auth.conf says: auth_mechanisms = plain Change it to: auth_mechanisms = plain login 2) Exim Configuration Add to /etc/exim/exim.conf in "AUTHENTICATION CONFIGURATION": dovecot_login: driver = dovecot public_name = LOGIN server_socket = /var/run/dovecot/auth-userdb server_set_id = $auth1 dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-userdb server_set_id = $auth1 auth_advertise_hosts = * Restart the Exim and Dovecot Service ROOT > service exim restart ROOT > service dovecot restart Done !!! Hope that was a Quick Trick. Webuzo Demo : http://demo.webuzo.com/enduser