How to securely send docs for Tax filing to my accountant electronically?

My Tax situation is a bit complicated and wasn’t able to find the accountant with expertise in my small town, I hired an accountant who works remotely and wants me to send him docs electronically. I was hesitant to send docs over email, accountant suggested to zip the docs and password protect it or use “box” cloud sharing. Do you guys have a better suggestion ?

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