diff --git a/conf/map/battle/feature.conf b/conf/map/battle/feature.conf
index 946bd00ed20..71601ee675e 100644
--- a/conf/map/battle/feature.conf
+++ b/conf/map/battle/feature.conf
@@ -61,10 +61,9 @@ features: {
 	rodex: true
 
 	// Allow usage of "Account Mail" box in RoDEX?
-	// Requires: 2016-03-16aRagexeRE or later
-	// This is disabled in client-side in some client versions
-	// Disabled by default
-	rodex_use_accountmail: false
+	// Requires: 2016-03-16aRagexeRE (+ patch) or later, 2016-03-23aRagexe or later, any zero client
+	// For RE clients, it requires client patching and you must also uncomment ENABLE_RODEX_ACCOUNT_MAIL_RE_PATCH in src/config/core.h
+	rodex_use_accountmail: true
 
 	// Allow Homunculus autofeeding
 	// true:  enable (Default)
diff --git a/doc/script_commands.txt b/doc/script_commands.txt
index ac1c5071129..08ddf2b376d 100644
--- a/doc/script_commands.txt
+++ b/doc/script_commands.txt
@@ -9718,6 +9718,9 @@ For examples of usage, see /doc/sample/npc_rodex.txt
 rodex_sendmail2 and rodex_sendmail_acc2 are more flexible versions.
 Check getitem2 command for more information of the extra parameters.
 
+Important: rodex_sendmail_acc (and rodex_sendmail_acc2) requires clients from 2016-03-23 or newer.
+  Additionally, it requires enabling "rodex_use_accountmail" on conf/map/battle/feature.conf.
+
 ---------------------------------------
 //=====================================
 7 - Instance-Related Commands
diff --git a/src/config/core.h b/src/config/core.h
index 534a10b74fa..72b0a6cc5f9 100644
--- a/src/config/core.h
+++ b/src/config/core.h
@@ -100,6 +100,10 @@
 /// Uncomment for use with Nemo patch ExtendOldCashShopPreview
 //#define ENABLE_OLD_CASHSHOP_PREVIEW_PATCH
 
+/// Uncomment to allow RE clients to enable RoDEX "Account Mail".
+/// RE clients requires Nemo patch for RoDEX Account Mail to work.
+//#define ENABLE_RODEX_ACCOUNT_MAIL_RE_PATCH
+
 /// Uncomment to allow flinch animation and walk delay to be synced
 /// Reduces positional lag when getting hit
 //#define WALKDELAY_SYNC
diff --git a/src/map/battle.c b/src/map/battle.c
index c2847c5ad29..290c8317e3c 100644
--- a/src/map/battle.c
+++ b/src/map/battle.c
@@ -8013,6 +8013,18 @@ static void battle_adjust_conf(void)
 	}
 #endif
 
+#if !(PACKETVER_MAIN_NUM >= 20160323 || (PACKETVER_RE_NUM >= 20160316 && defined(ENABLE_RODEX_ACCOUNT_MAIL_RE_PATCH)) || defined(PACKETVER_ZERO))
+	if (battle_config.feature_rodex_use_accountmail == 1) {
+#ifndef BUILDBOT /* Don't show these warnings to CI */
+		ShowWarning("conf/map/battle/feature.conf:features/rodex_use_accountmail RoDEX account mail is enabled but it requires 2016-03-16 RagexeRE / 2016-03-23 Ragexe or newer, disabling...\n");
+#ifdef PACKETVER_RE
+		ShowWarning("conf/map/battle/feature.conf:features/rodex_use_accountmail For RE clients, you should also enable ENABLE_RODEX_ACCOUNT_MAIL_RE_PATCH\n");
+#endif // PACKETVER_RE
+#endif // !BUILDBOT
+		battle_config.feature_rodex_use_accountmail = 0;
+	}
+#endif // date check
+
 #if !(PACKETVER_MAIN_NUM >= 20161130 || PACKETVER_RE_NUM >= 20161109 || defined(PACKETVER_ZERO))
 	if (battle_config.enable_refinery_ui == 1) {
 		ShowWarning("conf/map/battle/feature.conf refinery ui is enabled but it requires PACKETVER 2016-11-09 RagexeRE/2016-11-30 Ragexe or newer, disabling...\n");
diff --git a/src/map/script.c b/src/map/script.c
index 54fa7993f1b..3bd61ee1a2f 100644
--- a/src/map/script.c
+++ b/src/map/script.c
@@ -27269,6 +27269,9 @@ static bool buildin_rodex_sendmail_sub(struct script_state *st, struct rodex_mes
 	int receiver_id = script_getnum(st, 2);
 
 	if (strcmp(func_name, "rodex_sendmail_acc") == 0 || strcmp(func_name, "rodex_sendmail_acc2") == 0) {
+		if (battle_config.feature_rodex_use_accountmail == 0)
+			ShowWarning("script:rodex_sendmail_acc: You are sending an account mail while \"feature_rodex_use_accountmail\" is disabled. Players may not be able to view it.\n");
+
 		if (receiver_id < START_ACCOUNT_NUM || receiver_id > END_ACCOUNT_NUM) {
 			ShowError("script:rodex_sendmail: Invalid receiver account ID %d passed!\n", receiver_id);
 			return false;