We would just remove any attachments that are not required or already saved elsewhere (eg. NAS). Usually anything greater than about 1 or 2mb.
We have about a dozen users with most having a 2gb quota and a few 5gb quota.
Nethserver running on a vm.
An example would be a large upcoming job where someone may send a heap of plans (eg. 10mb total). We would be saving them elsewhere anyway (shared NAS storage that gets backed up daily), but may want to keep the "thread" of the email conversation in the long term without the 10mb of attachments.