CSSMTP does not provide SMTP listener support. CA Spool requires that a SMTP server is listening on a port, to send the emails to that server. SMTP is a protocol that runs over TCP/IP. CA Spool is configured with a TCP/IP address and port number.
. From the IBM Website:
CSSMTP has been designed to support z/OS users of SMTPD that create mail on the JES spool data set using batch jobs or that use SMTPNOTE for delivery to the Internet.
The mail messages you send today using SMTPD can probably be sent with CSSMTP. However, CSSMTP does have differences from SMTPD, and might not be able to accommodate everyone.
CCSMTP does not support SMTP server function, as CCSMTP is a mail-forwarding SMTP client application and is not a fully capable MTA.