Some implementations of Unix support a higher level of security called C2. In general, such sites are governmental or industrial where security is of high concern. SecureWare is a commercial add-on available for many architectures, most notably SCO Unix.

Now that SCO has split into two new companies, SecureWare is no longer available. This SECUREWARE compile-time macro has been retained, however, because those sites that have already installed it will use this macro.

If sendmail is built with this SECUREWARE compile-time macro defined, it will perform delivery under the identity of the luid of the recipient. In general, this SECUREWARE compile-time macro is correctly defined for those systems that are known to use it.

If you are running a precompiled version of sendmail, you can determine whether SECUREWARE was included by using the -d0.10 debugging switch (-d0.1) (if it appears in the list, support was included).