Here's some interesting stats about e-mail encryption both in and out of gmail.
https://www.google.com/transparencyreport/saferemail/?hl=en
The second (inbound) stat is especially interesting, showing that right now about 54% of other mail server-to-server communication is now encrypted (either opportunistic or mandatory)
When that day comes that mail server-to-server communication has reached 75% threshold, Im going to switch Postfix smtp_tls_security_level setting from "may" (opportunistic TLS) to "encrypt" (mandatory TLS encryption) and just ignore the rest of 25% that still(!) insist using unencrypted mail delivery between mail servers.
If you are your companys CEO or CIO ask yourself if your company is using e-mail encryption?
After all, do you want your competitor that work with government and it's three letter agencies to read your business mails?