Well it was a thought.
When I first starting using this digest plugin, Bluehost thought I was sending spam from my server, which is a no no for hosting. They were blocking all outgoing mail, ALL OF IT, from my blog. That included all the bbPress notifications. It took days to figure this all out. I had to fill out a form that required me to list the names of all the moderators getting notifications and attest that I had permission from them to send them these bulk notifications. What a mess. They treated this like a very serious violation and were about to lock out my account.
We help owners care for very sick dogs and even missing a few notifications can mean a dog might die without our help. It was very stressful.
Hope you figure this out. Tell me more about DNSExit. Would this be something I can use with my shared server on Bluehost?