How do I schedule different Leads to send emails on different date ?
When you want to schedule emails to go on pre-determined date for individual leads so that all leads won't be scheduled on single day.
What should be done when a user leaves an organisation ?
When a user leaves an organisation, you can remove that user from 7Targets too by using “Remove from Org” action under Organisation->Org Users.
It is demonstrated in the following image.
This action lets you assign the leads of this user to some other user in the organisation, like handing over those leads to some other user in the org.