The following command runs sendmail in rule-testing mode:
 If you get an error such as "sendmail: Address test mode not supported," you are probably not running the real sendmail. Some programs, such as Netscape's Internet Mail Server, masquerade as sendmail without letting you know that they are doing so. If this offends you, complain to the vendor of the imposter.
% /usr/sbin/sendmail -bt
At first, the output produced by this command line prompts you like this:
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> >
The "ruleset 3" statement says that, beginning with V8 (and IDA) sendmail, the canonify rule set 3 is no longer automatically called when rule sets are listed at the prompt. We cover this property in detail in Section 8.6.2.
Prior to V8 sendmail, rule-testing mode could be used only to test addresses. But beginning with V8.7 sendmail new functions were added. To see a summary of those functions, enter a ? character followed by a RETURN at the > prompt. The output, which we reproduce next, lists and gives a brief description of each function. Note that the numbers to the right refer to sections in this chapter and are not a part of sendmail's output:
> ? Help for test mode: ? :this help message. .Dmvalue :define macro `m' to `value'. Section 8.2.1 .Ccvalue :add `value' to class `c'. Section 8.2.2 =Sruleset :dump the contents of the indicated ruleset. Section 8.4.1 =M :display the known mailers. Section 8.4.2 -ddebug-spec :equivalent to the command-line -d debug flag. $m :print the value of macro $m. Section 8.3.1 $=c :print the contents of class $=c. Section 8.3.2 /mx host :returns the MX records for `host'. Section 8.5.2 /parse address :parse address, returning the value of crackaddr, and Section 8.5.5 the parsed address (same as -bv). /try mailer addr :rewrite address into the form it will have when Section 8.5.6 presented to the indicated mailer. /tryflags flags :set flags used by parsing. The flags can be `H' for Section 8.5.4 Header or `E' for Envelope, and `S' for Sender or `R' for Recipient. These can be combined. `HR' sets flags for header recipients. /canon hostname :try to canonify hostname. Section 8.5.1 /map mapname key :look up `key' in the indicated `mapname'. Section 8.5.3 /quit :quit address test mode. V8.10 and above rules addr :run the indicated address through the named rules. Section 8.6 Rules can be a comma-separated list of rules. End of HELP info >
This help output is contained in the helpfile file, the location of which is defined by the HelpFile option (HelpFile). If that option is not defined, or if the file specified does not exist, you will get the following error message instead of help:
 Prior to V8.10, this file was called sendmail.hf.
Sendmail 8.12 -- HELP not implemented
Help for rule-testing mode requires that the helpfile both exist and contain lines that begin with:
If you installed a new sendmail but did not install the new help file (thus causing the old file to be used), you might see this error:
HELP topic "-bt" unknown
The solution here is to upgrade your helpfile file to the newest version.
Note that each function listed in the help output will also produce a usage message if it is executed with no arguments. Consider the /try function, for example:
> /try Usage: /try mailer address >
This parallels the syntax shown in the earlier help output. These mini-usage messages can effectively replace the helpfile file in case it is missing.
Finally, note that, although address testing was not listed in the help output for V8.7 sendmail, it still existed.