The -b switch instructs sendmail to "Become"/operate in a mode.
The -d0 switch, instructs sendmail to produce debugging information.
The level .11 prints more information than the default level of .1 .
The -bp switch instructs sendmail to print the contents of the queue.
$ sendmail -d0.11 -bp
You can verify aliases with the -bv switch:
$ sendmail -bv root
To run sendmail verbosely, use the -v switch:
$ cat /dev/null | sendmail -v root