Just returned to DT3 after a dalliance with Windows! All setup well and went to the Import sidebar and clicked on Apple Mail and the folder list displayed as expected.
I imported several hundred messages without an issue.
Clicking on a folder that contained 1147 messages and got the spinning busy mousetip but the program was still running. After well over an hour no email was listed and the spinning continued.
I moved away form the Import sidebar and close DT3 and restarted.
Now whenever I select the Import sidebar DT3 crashes!
Using Big Sur with latest version of DT3 on a 2019 16" MacBookPro with 1TB drive and 16GB of memory.
For crashes DT generally recommend opening a support ticket - I’d guess Jim will be at work today (he might just have tomorrow off), so I think that might be your best bet.
(From the manual: If DEVONthink crashes while it’s running, please hold the ⌥ Option key and choose Help > Report Bug.)
(And from the blog: We are spending the holidays with our families and friends, away from our keyboards. We do check our email and support tickets but we might reply slower than usual. We’ll all be back for you on January 7th, 2021.)
Did it crash or was it unresponsive/frozen?
My apologies; I started a ticket as suggested by Blanc and Jim suggested the approach
Quit DEVONthink 3.
Enable Full disk access and all Automation requests for DEVONthink 3 in System Preferences > Security & Privacy > Privacy.
In the Finder, hold the Option key and choose Go > Library.
Go into the Mail/Bundles folder and delete the DEVONthink.mailbundle.
Relaunch DEVONthink 3 and install the Mail plugin from DEVONthink 3 > Install Add-Ons.
Relaunch Mail and enable the plugin via Apple Mail’s Preferences > General > Manage Plug-ins.
All is now fine!