if the mail server running is mail enable, .....go to the mail enable administrator,..go to messaging centre...go to post offices.....check whether the domain is existing in the post office...if not ..right cick and add a new post office from the mail enable admin.....thats how u add a mail domain from the server backend.....
if the domain is existing...check whether the control panel and the post office shows the same number of mail boxes..if anything is missing..add it depeneding on where it is missing...
rememeber removing the domain name from the domain table will do no good as there are more tables such as limits, hosting, data_bases, accounts, sys_users etc that are dependent on the domain table.
If the entry for the domain is not removed from the hosting table, then once an account is cancelled ..there will be problems when the IP of the cancelled domain is assigned to a new domain....
so try to resolve the issue by looking at the error message and removing from the db must be the last resort