The confSHELL macro is used to assign a value to the SHELL= directive in the created Makefile. That directive determines the shell that will be used to execute each command. The default is /bin/sh for most systems, and /usr/bin/sh for a few. In the extremely rare circumstance that the Bourne shell is not available in this standard location, or if you wish to use a different shell for building sendmail, you can redefine the shell using this confSHELL macro. For example:

define(`confSHELL', `/usr/local/bin/sh')

Note that use of any shell other than the Bourne shell might have unexpected results. Also note that the -E switch to Build cannot be used to pass this value in the environment.