This is an easy one:
(compat/sendmail/sendmail.c, around line 375)
(wdiff format -- that's wisner diff)
                if (!binary) {
!                       for (; optind < argc; ++optind) {
+                               cp = strchr(argv[optind], '\0');
+                               if (*--cp == ',')
+                                       *cp = '\0';
!                               (void) fprintf(mfp, "to %s\n", argv[optind]);
!                       }
                }