Group email forwarding.
Mail forwarding would be a useful feature for business accounts. However it seems that it causes problems with encryption. So why don't you do what Tutanota - aka your biggest rival - is doing and add, what they have dubbed, "Group" account. This allows you to create a group let's say "sales@---.com". Then you can add users to this group. So now when a message is sent to the group mail address (aka. sales) it is sent to all members in that group AND they can all respond through the sales email, to reply to the original sender! Brilliant!
Why? That's because it is something business users find imperative!
So please rethink the importance of mail forwarding and other ways to implement such a crucial-for-business tool.
With love and appreciation for the fantastic service you provide.