SMTP Relay capability allows organizations to use Exchange Online as an SMTP service for mail originating outside of the Exchange Online environment, for example SMTP-enabled applications such as fax servers. With the deployment of the August Service Update complete, SMTP clients can connect to Exchange Online SMTP servers and authenticate using Microsoft Online Services user credentials to send mail. The connection requires Transport Layer Security (TLS). To connect to the Microsoft Online Services SMTP server, open the SMTP client application and provide the following information.