sendmail: from Vladimir:

Here comes the third part of compatibility patch for sendmail.
* Introduced new safe_getdomainname() -- will it be useful?
* Fixed SEGV if sender address is missed. Should snoop for sender address in mail headers?
* More compat: use HOSTNAME instead of HOST when no server is explicitly specified.
* crond: fixed mail recipient address.

function                                             old     new   delta
safe_getdomainname                                     -      56     +56
sendgetmail_main                                    1937    1946      +9
grep_file                                            846     850      +4
crond_main                                          1423    1425      +2
xstrtoull_range_sfx                                  295     296      +1
utoa_to_buf                                          110     108      -2
passwd_main                                         1053    1049      -4
sv_main                                             1234    1228      -6
parse_expr                                           841     833      -8
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/4 up/down: 72/-20)             Total: 52 bytes

libbb/safe_gethostname.c

@@ -48,6 +48,19 @@ char* FAST_FUNC safe_gethostname(void)
 
 	/* Uname can fail only if you pass a bad pointer to it. */
 	uname(&uts);
-
-	return xstrndup(!*(uts.nodename) ? "?" : uts.nodename, sizeof(uts.nodename));
+	return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
+}
+
+/*
+ * On success return the current malloced and NUL terminated domainname.
+ * On error return malloced and NUL terminated string "?".
+ * This is an illegal first character for a domainname.
+ * The returned malloced string must be freed by the caller.
+ */
+char* FAST_FUNC safe_getdomainname(void)
+{
+	struct utsname uts;
+
+	uname(&uts);
+	return xstrndup(!uts.domainname[0] ? "?" : uts.domainname, sizeof(uts.domainname));
 }