Employers that care about this will simply ban origination of E2E secure messages from their networks. Plenty of large companies already ban web mail providers entirely, for similar reasons. So this isn't much of a factor in adoption of encrypted mail.
Right but my point is, big corporations are actively opposed to E2E secure messages and that's a barrier to adoption.
Few if any big companies are going to be sending you GPG/PGP encrypted or signed email or be willfully receiving it. Take the Fortune 1000 off the list of potential secure email users and you've got a large portion of the professional class who won't know how to use this technology. I think that's a barrier to adoption.
