cPanel has introduced an auto-discover SRV into zone files for domains that are apparently in /etc/remotedomains with the new WHM upgrade.
An additional SRV line is added that send email clients to a cPanel page (cpanelemaildiscovery.cpanel.net) rather than to their Echange server.
They have added a ‘beta patch’ in this forum link. In order to disable the autoconfig/autodiscovery support on remote domains, please see the info located here:
You do need to be in the correct sub-directory as shown on this page to successfully run that patch command.