Only message headers are automatically downloaded to your computer. If you have a slow network connection, you can use this option to improve performance. Secure Sockets Layer (SSL) is an encryption technology that helps improve the security of the account. To be able to edit the port number that follows the server address, select this check box. If Outlook cannot automatically detect your Exchange server, you can enter its address here. To access these settings, click Outlook > Preferences > Accounts, select the Exchange account, and then click Advanced. Settings include options for changing port numbers, using SSL, downloading message headers, and setting server addresses.

The following table provides information and tips for entering advanced Exchange settings. Outlook for Microsoft 365 for Mac Outlook 2021 for Mac Office 2021 for Mac Outlook 2019 for Mac Office 2019 for Mac Outlook 2016 for Mac Office 2016 for Mac Office for business Office 365 Small Business More.