Outlook for Mac clients cannot connect to Exchange Server
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Applies to: Outlook 2016 for MacOutlook for Mac for Office 365Outlook for Mac 2011
You cannot connect to a server that is running Microsoft Exchange Server from a Microsoft Outlook 2016 for Mac or Outlook for Mac 2011 client after disabling Secure Sockets Layer (SSL) on the server.
The connection failure occurs because Outlook for Mac uses SSL to establish communication with an Exchange server. When SSL is disabled and secure renegotiation is implemented as defined in RFC 5746, Outlook requires the server to be in Compatible mode so that the session can be renegotiated from SSL to Transport Layer Security (TLS).
Configure the Exchange server to support Compatible mode by using the instructions from KB article 980436 . This allows the Outlook for Mac client to establish a connection by using the SSL protocol and then renegotiate by using TLS. This method allows Outlook for Mac to connect to the server even when SSL 2.0 and 3.0 are blocked. If you are using a security product such as Microsoft Forefront Threat Management Gateway (TMG) for managing connections to Exchange Server from outside your company, you will need to configure your TMG server using KB article 980436 . External connections to Exchange Server may be blocked if this server is in Strict mode.
NoteDo not configure the server to use Strict mode, as this prevents the Outlook for Mac client from connecting to the Exchange server.
For more information about SSL/TLS Renegotiation, please review this TechNet blog post.