Originally Posted by mturillo
Any idea? Is it a BUG of ISPConfig?
I dont think its a bug. If ISPConfig reports a duplicate email address, then there must be a duplicate email address in the database. Please have a look if thie email address that you want to create exists already in the database table isp_isp_user
Be aware that you might have added this email address as an alias to one of the other accounts, which will have the same result as if you have added it as mailbox.