Recently one of the institutions I teach at outsourced its email system to a "cloud" provider. This involved the transfer of tens of thousands of email accounts from about 100 mail servers. Much of the benefit of this project came from tracking down all the email servers and accounts (the outsourcing is not necessarly a good idea).
The email rehosting went reasonably smoothly, but one of the surprises was how much email people keep and the inappropriate uses it is put to. Email systems are intended for communication between people, not for long term storage of official records. Large and important documents should be held in corporate management systems, not scattered throughout the email. There are other more appropriate communication channels for specialized tasks, such as teaching and collaboration.
For communication with a group there are many products which will let you collaborate. Some of these are design for specific purposes, such as Moodle's forums, for student discussion. There also also web based tools for one-to-one communication with students. These can seem more cumbersome than email, but all the communication is neatly kept in the Learning Management System, indexed by student, where another teacher can pick it up if needed.
Large amounts of email traffic is generated sending around drafts of documents. This can cause problems when you loose track of what is the latest version, or if an email goes astray and a draft gets into the wrong hands. A better approach is to upload the document to a central management system and have it send everyone an alert. They then log into the central system to get the latest version. If an email goes astray, no harm is done as an unauthorized person will not have access to the central system.