Activity Log Digests

Since upgrading to 2.6 from 2.0, users are receiving Activity Log Digests when they were not before. The biggest issue is that they are being sent form [database username]@server.[example].com. Mime Mail is set to a different email and regular site notifications are being sent from that email address. How to I at least turn off Activity Log Digests (as they are creating to much inbox material along with notifications) or find where to switch the generator to use Mime Mail address