Email bouncing when sent to OmniFocus 3 via Mail Drop

Sorry for not seeing this sooner; these forums are for customers to chat with each other, as noted in the welcome message:

If you’re still having trouble sorting out the Mail Drop functionality on our sync server, please email our support humans at omnifocus@omnigroup.com. We try to answer every emailed question within one business day, so you’ll get a response much faster that way!