Prior to V8 sendmail the -bz command-line switch caused sendmail to build (or rebuild) its frozen configuration file (now obsolete). The frozen configuration file was just a simple image of sendmail's variables after it had read and parsed the configuration file. The purpose of the frozen file was to enable sendmail to start up more swiftly than it could when parsing the configuration file from scratch.^[9]

^[9] In practice, freeze files helped you only on systems with very fast I/O relative to their CPU speeds. Although this was true in the day of the VAX 11/750, improvements in processor technology have reversed this tradeoff.

The -bz command-line switch is obsolete. If you use it with V8 and higher sendmail, you will see this error message:

Frozen configurations unsupported