Required Email field

Each person that has a login is indeed required to have an email address. The email address is the unique identifier and is used to help with support, lost login information, etc. As a workaround you could enter a fake email address. Also via email support around this topic it sounded like part of the issue is being able to assign tasks without having someone work on them just yet. This can be accomplished by assigning the task to no assignee until the task is ready to be worked on. When ready the assignee can be changed from none to the appropriate person. We actually use a similar methodology with backlog tasks where we assign tasks to a backlog module with no due date and no assignee. Periodically we go through the backlog and make the tasks actionable by assigning them to a person with a due date. Hope it helps.