AzureAD connect rejects valid o365 admin account with special character before @
AzureAD connect attempts to validate the username entered for the admin account, but it rejects valid usernames which contain a special character in the position immediately proceeding the @.
For example, it is possible to create an azuread/o365 user account with the username of 'firstname.lastname@example.org'. This is a valid user account and email address, but when it is entered the AzureAD connect tool rejects it with an error indicating that the format is incorrect.
Please fix the input validation rules so that they don't reject usernames with special characters in the position prior to the @.