Why doesn't my server send mail from a domain's dedicated IP address or server name when ASSP is running?
SNI (Server Name Indication) allows the server to send mail using dedicated IP addresses and server names. You must enable the SNI functionality in ASSP in order for ASSP to send using SNI.
Please note that ASSP is third-party software for which cPanel does not provide support. You can read about how to enable SNI for ASSP in their documentation here, under the Does ASSP support SSL SNI? section: