Twitter has upgraded to an encrypted (TLS or SSL) connection using STARTTLS. StartTLS encrypts emails as they transit between sender and receiver and is designed to prevent snooping. It also ensures that emails you receive from Twitter haven’t been read by other parties on the way to your inbox if your email provider supports it. Twitter admire Gmail and AOL Mail, who are already supporting TSL encryption and encouraging other services to enable it, “Together, we can protect the privacy of every user”
Source: https://thehackernews.com/2014/03/twitter-enables-starttls-for-secure.html