Opportunistic TLS vs Forced TLS for SMTP
Tuesday, January 23rd, 2024Email sometimes seems like magic because of how quickly messages are transmitted across the internet. While the rapid delivery speeds justify this presumption, a lot must happen for an email to reach you. Email sending relies on a protocol called the Simple Mail Transfer Protocol (SMTP) to make its way across the internet to your recipient’s server. From there, the recipient uses another protocol, such as ActiveSync, POP3, MAPI, IMAP, or a Web-based interface, to pick it up and read it.
Unfortunately, these protocols aren’t always secure by default. Under its original design, emails are sent as plain text. Anyone along the email’s journey can see (and even change) their contents. This can include those in charge of the servers, the government, and even hackers that intercept the data.
Thankfully, engineers are aware of this glaring security hole, and they have introduced several mechanisms that can be leveraged to protect email. This article reviews how SMTP TLS works and the differences between opportunistic TLS and forced TLS.
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