Fail to create mail account.

Fail to create mail account.

I want to create a mail account but it fails with the following message.
Given emailId already exists.
I believe this is because I deleted a   mail account which had  the exact same name.
I tried again, after deleting and re-creating domain & organization, but failed again.


The reason why I deleted the mail account is the migration problem, but I want to solve this problem now, because I am nervous that until this problem is solved I cannot get any email.