We get a ton of MSP's and agencies who share sensitive data with their clients just over email, sms, chat, Whatsapp, ... which is a big red flag of course. Do you have systems in place? We created a solution ourselves, but I'm wondering about your solutions.
Until recently I'd say only a phone call, but even that is quickly going by the wayside. Otherwise... If I'm an MSP, my remote control software is almost the only thing I trust anymore, and that's had problems.