Starting in the Solaris 10 1/06 release, sendmail supports
SMTP using Transport Layer Security (TLS). For more information, see the following:
Support for Running SMTP With TLS in Version 8.13 of sendmail
How to Set SMTP to Use TLS
For a complete list of features in the Solaris 10 1/06 release, see Oracle Solaris 10 9/10 What’s New.