When rolling out self service and sending welcome emails, every time you add a new starter, as long as you put their email address in their Personal tab, the system will send them a welcome email.
If you choose to send welcome emails from system settings, the system will send a welcome message with login details to all employees who are new to People, meaning all users who haven't logged in before to PeopleHR.
The Contacts tab is for recording purposes and the welcome email will be triggered only for those having an email address within their Personal tab and who did not log in before.
📌Note: If you removed their email addresses from their Personal tab you can click the clock icon next to it and see the history, meaning you'll still have access to what's been there as the history of changes can not be amended or deleted.