if users will be create with maximum allowed character count email address, users can't delete from system.
if user will be delete from system, the email-address of deleted user stored in username field of database with added timecode.
As result of this the length of username in table
is to short to store that information.
The user's removal leads to a database exception
to correct that problem, the email address validation must be customized or username field must be larger than 100 characters