Email Settings Auto Discovery
Auto Discovery allows email clients that support Microsoft Outlook and Mozilla Thunderbird’s AutoDiscovery and AutoConfig protocols to automatically configure their email settings. When this feature is enabled, support is added for Outlook 2010, Outlook 2007, Postbox, Mozilla Thunderbird, and KDE Kmail.
Query Apache for ‘nobody’ senders
Query Apache for ‘nobody’ senders enables the mail delivery process to query the Apache server to determine the true sender of a message when the user who sent the message is ‘nobody’. This feature requires an additional connection to the webserver for each message that is sent with the user account ‘nobody’ (PHPsuExec and mod_ruid2 disabled). This option is more secure, but not as fast as trusting X-PHP-Script headers.