When accessing webmail I am redirected and asked to log in a second time.

Symptoms

When accessing the Webmail interface, I am redirected and asked to login a second time.

Description 

Accessing the webmail interface via IP:2096 or hostname.tld:2096 asks for the login details after the initial redirect.

Workaround

Make sure that your account is not listed in cPhulk as this can prevent users from logging into the interface.