Well, since I was 11B I didn't spend enough time in the office to pick up on all the intricacies involved.
And thank you for your service! We're all on the same team! 
emails are "signed" these days, if you set them up that way. I work on an Army post, and all the stuff I send gets signed. My CAC card, (ID card with embeded chip and magnetic strip) is used to verify that I'm me when I send an email. Of course if you don't have access to the server which verifies the signatures (via a public key, you sign with your private key. It would take too long to explain, and I only kinda sorta undertstand it myself.
But you shouldn't let an old guy teach a young'un like you about modern new fangled stuff.
I was on active duty, as a very junior officer, from '73 to '75.
Well, since I was 11B I didn't spend enough time in the office to pick up on all the intricacies involved.
And thank you for your service! We're all on the same team!