I'm offering here, for anyone interested, my patched version of
sendmail/rmail (version V1.17-beta.31{ask@castrov.UUCP/10} Aug 07 1994).

The main motivation for the changes was to comply with the strong 
"SmartUUCP" requirements of my local domain.  These requirements go 
beyond the initial "SmartUUCP" implementation in sendmail 1.17.31.

At the same time a few other enhancements were made.  A new concept
in config variables is introduced.  "Host-specific" variables are
of the form "Host-xxx-variable".  They are used in in preference
of the ordinary "host-non-specific" variables when doing work for
the system specified in "xxx".  Sendmail uses two host-specific
variables: Host-xxx-SmartUUCP and Host-xxx-MaxRMailLen.

Changes:
--------

*  When sending a message to a "SmartUUCP" neighbor, generate the Envelope 
   "rmail " addresses in @-format rather than !-format.  This is required 
   by some "SmartUUCP" sites.

* Support per-host config variables for the SmartUUCP flag of the form 
  Host-xxx-SmartUUCP, where xxx is the neighbor.  Translate messages to 
  and from "SmartUUCP"-format, so we can act as a bridge between the often 
  incompatible worlds.

* Support per-host config variables for the MaxRMailLen value of the form 
  Host-xxx-MaxRMailLen, where xxx is the neighbor.  Each neighbor can have 
  a value tuned to their limitations rather than being restricted to the 
  smallest value of all neighbors.

* Be more efficient about packing addressess onto the rmail line.  We used 
  to send off messages to *all* neighbors as soon as the accumulation of 
  addresses for *one* neighbor was full.

* Tell UUX if we are running as "postmaster".  This will appear in the 
  remote system's uulib:logfile.

* Record the SUBVERSION in the Received: line, for easier reporting of bugs.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                29258   52208  56.0% -lh5- 97f4 Aug  7  1994 SendMailWuth10/c/sendmail
[generic]                 3186    7600  41.9% -lh5- b082 Aug  9  1994 SendMailWuth10/Man/sendmail
[generic]                  415     966  43.0% -lh5- bc61 Aug 15  1994 SendMailWuth10/PGP-Sig/check.md5
[generic]                  152     152 100.0% -lh0- d670 Aug 15  1994 SendMailWuth10/PGP-Sig/check.md5.sig
[generic]                  669     669 100.0% -lh0- 0721 Apr 27  1994 SendMailWuth10/PGP-Sig/Wuth.pgp
[generic]                 1199    2396  50.0% -lh5- 54f6 Aug 15  1994 SendMailWuth10/ReleaseNotes
[generic]                 1922    5399  35.6% -lh5- a3c9 Aug  7  1994 SendMailWuth10/src/lib/config.c
[generic]                 1060    2356  45.0% -lh5- b60b Aug  7  1994 SendMailWuth10/src/lib/DMakefile
[generic]                 1158    2139  54.1% -lh5- ffc3 Aug  8  1994 SendMailWuth10/src/lib/version.doc
[generic]                  677    1452  46.6% -lh5- a4cd Aug  7  1994 SendMailWuth10/src/sendmail/DMakefile
[generic]                21631   68613  31.5% -lh5- 4054 Aug  7  1994 SendMailWuth10/src/sendmail/sendmail.c
[generic]                   20      20 100.0% -lh0- 227f Jul 26  1994 SendMailWuth10/src/sendmail/TestCases/uulib.start/Domain
[generic]                   64     102  62.7% -lh5- e069 Jul 26  1994 SendMailWuth10/src/sendmail/TestCases/uulib.start/l.sys
[generic]                    0       0 ****** -lh0- 0000 Aug  7  1994 SendMailWuth10/src/sendmail/TestCases/uulib.start/MailLog
[generic]                    6       6 100.0% -lh0- 12e1 Jul 26  1994 SendMailWuth10/src/sendmail/TestCases/uulib.start/seq
[generic]                 4314    9708  44.4% -lh5- 3bc0 Aug  8  1994 SendMailWuth10/src/sendmail/version.doc
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total        16 files   65731  153786  42.7%            Aug 30  1994