I previously worked for a large Bank and they had authenticated email using Lotus Notes. While i would not recommend using that, it was nice to see them taking this serious. It was required to use it for every internal communication and actually made it seriously easy to use without knowing much about how it really works.
Its much easier to teach people to access their emails using a particullar application then it is to make them aware for phising attacks which sometimes can be very sophisticated.
While this does not work if you have to receive emails from unknowns, it is a no brainer to use something like this at a comapny level for all online communication. In my opinion not doing so is really careless behaviour especially for a tech company...
Microsoft Exchange allows for implementation of S/MIME encryption and signing that more or less "just works." There are some naggles (I've run into people before whose Outlook was S/MIME signing emails to external uses, and my Outlook would be upset about showing them since the external user's cert was signed by some internal CA I didn't trust - if I didn't know what was going on that have lead to a frustrating helpdesk call). But, overall, it's nearly transparent when everything is as it should be.
Unfortunately, outside of the world of these internal corporate email products the situation looks a lot worse. Reliably secure delivery of email to external users is a hard problem and most of the current solutions being used are really, really terrible.
Its much easier to teach people to access their emails using a particullar application then it is to make them aware for phising attacks which sometimes can be very sophisticated.
While this does not work if you have to receive emails from unknowns, it is a no brainer to use something like this at a comapny level for all online communication. In my opinion not doing so is really careless behaviour especially for a tech company...