At work, we use mail-system based encryption like Zix, IronPort or Voltage. Those solutions provide guaranteed encrypted transit to the recipients public network boundary. Depending on the content, the system either just ensures that messages travel via TLS or requires explicit authentication via a web interface.

In my personal life, I haven't used mail encryption since my college days with some crypto geek friends. I do have an OpenGPG card and public key published, but I mostly use it to encrypt data at rest on cloud storage platforms or USB keys.