sendmail, 4th Edition

_FFR...

Try using future features Tune with confENVDEF

Inside the sendmail code are pieces of new code, which can add new features, options, macros, and the like, that might appear in V8.13 and above versions of sendmail. You can include any of these new pieces of code by defining one of the following _FFR (For Future Release) m4 Build macros when building sendmail:

APPENDDEF(`conf_sendmail_ENVDEF', `-D_FFR_what''    ← affects sendmail only
APPENDDEF(`conf_makemap_ENVDEF', `-D_FFR_what')     ← affects makemap only
APPENDDEF(`confENVDEF', `-D_FFR_what')              ← affects all programs

Here, what describes the appropriate future item that you want to include (as found in the source). Consider the following example:

APPENDDEF(`confENVDEF', `-D_FFR_QUARANTINE=1')

Here, the _FFR_QUARANTINE m4 Build macro is defined so that the sendmail and mailstats programs can support queue quarantining of messages.

If you are running a precompiled binary of sendmail, you can determine whether any of the _FFR macros were defined when sendmail was compiled by using the -d0.13 debugging switch (-d0.13 on page 544):

% /usr/sbin/sendmail -d0.13 -bt
Version 8.14.1
 Compiled with: DNSMAP LOG MAP_REGEX MILTER MIME7TO8 MIME8TO7 NAMED_BIND
etc ...
  FFR Defines: _FFR_QUARANTINE          ← note
etc ...

Note that by running any of the sendmail suite of programs with an FFR defined, you are, in effect, acting as a guinea pig for the sendmail development team. You will be utilizing new features in production and, by doing so, can uncover bugs that ...