I'm sure reason #2 is why he's was so upset about turning over communications going back to 2015. Given things he's posted in a public forum, you can imagine what occurred in private emails.
@edpc Do you have your emails going back to 2015? Unless they could get them off my computer hard drive, no, wait, that wouldn't work as I have a different computer than in even 2016. Do you keep emails for years and move all of them to a new computer when that computer dies? I got this computer in about May of 2017. Mueller would start pulling his hair out trying to find my emails before that. Now, I have four computers but three have absolutely nothing of importance on them; the one I am using this minute is the new, major one, new last May. I dump emails regularly to keep them out of my inbox. Email receipts from buying something, I keep, but those are boring emails. If I was having clandestine emails, I would use whatever that is that actually removes them forever. Don't those type people do that so they won't get caught with "evidence"?
Those type people likely have trouble with having a phone. A phone today is like having your life on there. I had to learn more about my phone two days ago in order to download an "App" to connect to my wrist band that measures my heart beat and blood pressure. I realized that phone has invaded my life. In order to use the wrist band, my phone had to be smart enough to talk to the band or I could not use the wrist band. People with secrets should not have a phone.