In order to proactively manage issues with digest subscriptions, I would need a tool that:
1) Tells me what users have subscribed to which digests, and when they last received an emailed digest. This is necessary for when the user complains that he/she did not receive a digest and determine if the email was lost somehow in transit or was never sent.

2) Reproduce specific digest contents from past periods of time. This is also need to try to work out why a digest was not sent when the user believes a digest should have been sent.

3) A permanent repository of all digest messages sent to users from this institution. This is necessary for when digests are "lost in transit" and need to be recovered so that the user can act on information in the email.