After an upgrade or a fresh installation of GFI MailEssential the configuration does not accept the user credentials.
all supported environments
The credentials should be specified in the correct format , especially using the domain name as the format below: domain\account
The credentials were not entered in the correct format. If there are two administrator accounts for example, one local and one domain admin account GFI MailEssentials will be unable to guess which account is valid without including the domain name.