Active Exchange services, see Add Hosted Services, client software/hardware that supports TLS encryption.
|Exchange 2013 IMAP Settings|
|Encryption||SSL encryption is required.|
|SMTP Encryption||TLS* encryption is required.|
*Note that the outgoing, SMTP, server uses Transport Layer Security (TLS) to send mail. Not all mail clients, nor hardware (copiers, scanners) support TLS. TLS in short is a standard protocol that's used to provide secure Web communications on the Internet or intranets. It enables clients to authenticate servers or, optionally, servers to authenticate clients. It also provides a secure channel by encrypting communications. TLS is the latest version of the Secure Sockets Layer (SSL) protocol. If your device does not support TLS we recommend you setup a Split Domain configuration and use a basic mail account to send the mail.