Note: lists below have been updated as of 9/11/2015.
We are frequently asked how common is the support of SMTP TLS for securing inbound email delivery to recipients across the Internet. This is especially important for customers who need to be HIPAA compliant, as email transport encryption over TLS is sufficient for HIPAA compliant communications to end users, so long as the TLS is configured to be sufficiently strong.
While it is possible to tell who supports TLS, its is somewhat technical to do yourself. So, we have assembled a table with many of the popular free / public email domains in use across the Internet and indicate which currently (as of January 14th, 2015) support SMTP TLS for inbound email.
The results are surprising. A majority of domains these days do support TLS, and with Microsoft’s recent TLS implementation on its email domains (hotmail.com/live.com/outlook.com), this rounds out consistent TLS support (for inbound delivery–outbound may or may not be supported) for all of the most popular free email providers (e.g. aol.com, gmail.com yahoo.com, hotmail.com).
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