Gmail uses TLS, or Transport Layer Security, by default for all email communications, so all of your emails will use the standard encryption as long as the recipients also support TLS. But there's a way to add even more security to your Gmail emails, and you can use your iPhone's Mail app to do it. Apple has supported S/MIME, or Secure/Multipurpose Internet Mail Extensions, on iPhone since iOS 5 over ten years ago. S/MIME is a widely accepted cryptographic protocol for sending and receiving digitally signed and encrypted messages, and it works on top of Gmail's TLS system. S/MIME is similar... more
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