This is completely unscientific, but I am beginning to feel a sea change in how organizations are designing email management schemes.
The trend that I am seeing (and we'll use Microsoft Outlook / Exchange as the benchmark)is as follows:
1) Organizations reduce retention schedules to "big buckets" as much as possible. At bare minimum, the retention schedules are distilled functionally, rather than by department.
2) Creation of PSTs is banned. Generally, this involves a registry change that prevents the user from creating PST files.
3) All mail is server-based, with limited local replicas for offline use.
4) The organization pushes a core set of common folders to all employees. These folders are managed and set for retention periods. Generally, the common folders are used for short (60 - 90 days) and medium (2-3 years) retention periods for items that the user wants to keep transitionally. In addition, items foldered in non-managed user folders are treated in the same manner (generally the medium period).
5) The user can pull down additional folders from the retention schedule as required.
6) The user is instructed to file all records of the organization in the appropriate folder.
7) The Inbox and Sent folders are purged after 90 days (trending to one year). If the user has not filed an email that was in these folders, the email will be automatically deleted.
Thus, the trend is to group email as records (folders that map to retention schedule), transitional items (items that need to be kept for reference, but rarely more than a couple years), and non-records (items that are deleted immediately by the user or automatically after a brief period).
The auto-delete function deletes items into a holding folder for about a week (in the event that something is inadvertently designated for deletion) and then permanently deleted.
An interface to a legal hold process must suspend the auto-delete function.
Again, this is not scientific, but it reflects a trend that I am hearing from a number of colleagues.
Efforts to manage email in document management systems seem to be waning due to complexity.
Companies utilizing these processes see an initial spike in server email volumes, but the volumes tend to stabilize and decline once the retention controls come into play. Mail quota management is eliminated for the most part, although more sophisticated monitoring comes into play to see how employees are filing documents and how much space they are consuming.
Existing PSTs cannot be added to, but email within existing PSTs can be similarly managed and transferred to the Exchange server. Many organizations plan a transition period of several years for employees to manage needed email from legacy PSTs, then delete the PSTs.
It will be interesting to see how this turns out over the next several years.