Creation of new domain in Plesk fails with warning:
This domain name already exists
Domain already exists in Mail Server. As mail configuration for domain already exists, Plesk can not rewrite it.
Make sure that domain does not exist in Mail server. If domain exists, please remove it and try to create domain using Plesk interface again.
Example. To check if domain exists in Mailenable, you can the following way:
Start → All Programs → Mail Enable → MailEnable Administrator >> Messaging manager → Post Offices