If you are adding an employee that doesn't have an email address or will not need their own access so no email address needs to be added then be sure to use this format as their email.
noemail+the employees first name and second name @ewassist.co.uk(with no spaces e.g. email@example.com)
This will ensure that the employee never receives a welcome email.
When adding a new employee (People > Add) you can click the 'Set as NoEmail' button to add an employee that doesn't have an email address.
Anyone can have a new email address added to their account at a later date.