maxrcpt: if DISABLE_MAXRCPT is defined it skips the check

maxrcpt: error code changed to 452 due to RFC 4.5.3.1 (was 553). If DISABLE_MAXRCPT is defined it skips the check, otherwise outgoing messages from mailing lists would be rejected.

README.md

@@ -131,8 +131,10 @@ This distribution of qmail puts together netqmail-1.06 with the following patche
   https://nvd.nist.gov/vuln/detail/CVE-2023-51765). Enable bare LF by defining ALLOW_BARELF in tcprules.
 * Michael Samuel's maxrcpt patch
   allows you to set a limit on how many recipients are specified for any one email message by setting
-  control/maxrcpt. RFC 2821 section 4.5.3.1 says that an MTA MUST allow at least 100 recipients for each
-  message, since this is one of the favourite tricks of the spammer.
+  control/maxrcpt. [RFC 2821 section 4.5.3.1](https://datatracker.ietf.org/doc/html/rfc2821#section-4.5.3.1)
+  says that an MTA MUST allow at least 100 recipients for each message, since this is one of the favourite
+  tricks of the spammer. If DISABLE_MAXRCPT is defined it skips the check, as outgoing messages from mailing
+  lists would be rejected otherwise.
   https://notes.sagredo.eu/files/qmail/patches/maxrcpt.patch
 * Inter7's qmail-eMPF patch
   More info: https://notes.sagredo.eu/files/qmail/patches/empf.README

qmail-smtpd.c

@@ -141,8 +141,8 @@ char *arg;
 /* rbl: end */
 void err_maxrcpt()
 {
-  out("553 max rcpt limit exceeded (#5.7.1)\r\n");
-  qlogenvelope("rejected","max_rcpt_exceeded","","553");
+  out("452 max rcpt limit exceeded (#5.7.1)\r\n");
+  qlogenvelope("rejected","max_rcpt_exceeded","","452");
   flush();
 }
 void straynewline() { qlogenvelope("rejected","bad_newlines","","451"); out("451 See http://pobox.com/~djb/docs/smtplf.html.\r\n"); flush(); _exit(1); }
@@ -1056,6 +1056,7 @@ int addrvalid()
 /* rcptcheck: end */
 
 int checkrcptcount() {
+  if (env_get("DISABLE_MAXRCPT")) return 0;
   if (maxrcpt == -1) {return 0;}
   else if (rcptcount > maxrcpt) {return 1;}
   else {return 0;}