Sending sensitive documents over the internet

My accountant has gotten a taste for telework during the pandemic and has decided to only accept tax documents through the internet this year.

I was wondering which method I should use to send them? I believe most of her clients just put them in email attachments, but that's a no-go as I believe the servers the information passes through can capture that info very easily. In the past I've tried sending documents in apassword-protected winRAR file, but some people …

accept attachments clients documents email internet pandemic privacy send sensitive tax