Unwanted email scanning

I’m using DevonThink 3.0beta1. My default email client is Thunderbird, not Apple Mail. Whenever I start up DevonThink it wants to open Apple Mail and scan my email messages.

I don’t know why it wants to do this or how to turn it off. I’ve looked through Preferences and database settings, Applescript rules, Smart Rules, etc., and I can find nothing that’s invoking this or that controls this. Any idea where this is coming from?

The current version is public beta 2. Please update and see if the behavior persists. If it does, reboot the machine and see if it still persists.

Right after launching the application or after selecting View > Sidebar > Import? In addition, is Thunderbird selected as the default email client (see Apple Mail > Preferences > General)?