Ranked in these QuestionsQuestion Ranking
Pro Tasks can be interacted with via email
Redbooth allows creating and replying to tasks using email.
Pro Allows getting granular in how manage tasks
Redbooth allows creating task lists and subtasks and each item can have labels, comments, descriptions, attachments, allotted time, etc.
Con Collaborative features are behind a paywall
Group chat and video messaging requires a Premium account.