diff --git a/modules/um_callerid.c b/modules/um_callerid.c
index 89743598..74d4ce3b 100644
--- a/modules/um_callerid.c
+++ b/modules/um_callerid.c
@@ -44,49 +44,78 @@
 #include "supported.h"
 #include "logger.h"
 
-static int
-um_callerid_modinit(void)
-{
-	user_modes['g'] = find_umode_slot();
-	if (!user_modes['g'])
-	{
-		ierror("um_callerid: unable to allocate usermode slot for +g; unloading module.");
-		return -1;
-	}
-
-	user_modes['G'] = find_umode_slot();
-	if (!user_modes['G'])
-	{
-		user_modes['g'] = 0;
-
-		ierror("um_callerid: unable to allocate usermode slot for +G; unloading module.");
-		return -1;
-	}
-
-	construct_umodebuf();
-
-	add_isupport("CALLERID", isupport_umode, "g");
-
-	return 0;
-}
-
-static void
-um_callerid_moddeinit(void)
-{
-	user_modes['g'] = 0;
-	user_modes['G'] = 0;
-	construct_umodebuf();
-
-	delete_isupport("CALLERID");
-}
-
 #define IsSetStrictCallerID(c)	((c->umodes & user_modes['g']) == user_modes['g'])
 #define IsSetRelaxedCallerID(c)	((c->umodes & user_modes['G']) == user_modes['G'])
 #define IsSetAnyCallerID(c)	(IsSetStrictCallerID(c) || IsSetRelaxedCallerID(c))
+#define IsSetTalkThroughCallerID(c)	((c->umodes & user_modes['M']) == user_modes['M'])
 
 static const char um_callerid_desc[] =
 	"Provides usermodes +g and +G which restrict messages from unauthorized users.";
 
+
+struct CallerIDOverrideSession {
+	rb_dlink_node node;
+
+	struct Client *client;
+	time_t deadline;
+};
+
+static rb_dlink_list callerid_overriding_opers = { NULL, NULL, 0 };
+struct ev_entry *expire_callerid_override_deadlines_ev = NULL;
+
+static void
+update_session_deadline(struct Client *source_p)
+{
+	struct CallerIDOverrideSession *session_p = NULL;
+	rb_dlink_node *n;
+
+	RB_DLINK_FOREACH(n, callerid_overriding_opers.head)
+	{
+		struct CallerIDOverrideSession *s = n->data;
+
+		if (s->client == source_p)
+		{
+			session_p = s;
+			break;
+		}
+	}
+
+	if (session_p != NULL)
+	{
+		rb_dlinkDelete(&session_p->node, &callerid_overriding_opers);
+	}
+	else
+	{
+		session_p = rb_malloc(sizeof(struct CallerIDOverrideSession));
+		session_p->client = source_p;
+	}
+
+	session_p->deadline = rb_current_time() + 1800;
+
+	rb_dlinkAddTail(session_p, &session_p->node, &callerid_overriding_opers);
+}
+
+static void
+expire_callerid_override_deadlines(void *unused)
+{
+	rb_dlink_node *n, *tn;
+
+	RB_DLINK_FOREACH_SAFE(n, tn, callerid_overriding_opers.head)
+	{
+		struct CallerIDOverrideSession *session_p = n->data;
+
+		if (session_p->deadline >= rb_current_time())
+		{
+			break;
+		}
+		else
+		{
+			const char *parv[4] = {session_p->client->name, session_p->client->name, "-M", NULL};
+			user_mode(session_p->client, session_p->client, 3, parv);
+		}
+	}
+}
+
 static bool
 allow_message(struct Client *source_p, struct Client *target_p)
 {
@@ -105,7 +134,7 @@ allow_message(struct Client *source_p, struct Client *target_p)
 		return true;
 
 	/* XXX: controversial?  allow opers to send through +g */
-	if (MayHavePrivilege(source_p, "oper:message"))
+	if (IsSetTalkThroughCallerID(source_p) || MayHavePrivilege(source_p, "oper:always_message"))
 		return true;
 
 	if (accept_message(source_p, target_p))
@@ -227,11 +256,156 @@ h_hdl_privmsg_user(void *vdata)
 	data->approved = ERR_TARGUMODEG;
 }
 
+static void
+check_umode_change(void *vdata)
+{
+	hook_data_umode_changed *data = (hook_data_umode_changed *)vdata;
+	bool changed = false;
+	struct Client *source_p = data->client;
+
+	if (!MyClient(source_p))
+		return;
+
+	if (data->oldumodes & UMODE_OPER && !IsOper(source_p))
+		source_p->umodes &= ~user_modes['M'];
+
+	changed = ((data->oldumodes ^ source_p->umodes) & user_modes['M']);
+
+	if (changed && source_p->umodes & user_modes['M'])
+	{
+		if (!HasPrivilege(source_p, "oper:message"))
+		{
+			sendto_one_notice(source_p, ":*** You need oper:message privilege for +M");
+			source_p->umodes &= ~user_modes['M'];
+			return;
+		}
+
+		update_session_deadline(source_p);
+	}
+	else if (changed)
+	{
+		// Unsetting +M; remove the timeout session
+		rb_dlink_node *n, *tn;
+
+		RB_DLINK_FOREACH_SAFE(n, tn, callerid_overriding_opers.head)
+		{
+			struct CallerIDOverrideSession *session_p = n->data;
+
+			if (session_p->client != source_p)
+				continue;
+
+			rb_dlinkDelete(n, &callerid_overriding_opers);
+			rb_free(session_p);
+		}
+	}
+}
+
+static void check_priv_change(void *vdata)
+{
+	hook_data_priv_change *data = (hook_data_priv_change*)vdata;
+	struct Client *source_p = data->client;
+	const char *fakeparv[4];
+
+	if (!MyClient(source_p))
+		return;
+
+	if (source_p->umodes & user_modes['M'] && !HasPrivilege(source_p, "oper:message"))
+	{
+		sendto_one_notice(source_p, ":*** You need oper:message privilege for +M");
+		fakeparv[0] = fakeparv[1] = source_p->name;
+		fakeparv[2] = "-M";
+		fakeparv[3] = NULL;
+		user_mode(source_p, source_p, 3, fakeparv);
+	}
+}
+
+static void
+handle_client_exit(void *vdata)
+{
+	hook_data_client_exit *data = (hook_data_client_exit *) vdata;
+	rb_dlink_node *n, *tn;
+	struct Client *source_p = data->target;
+
+	RB_DLINK_FOREACH_SAFE(n, tn, callerid_overriding_opers.head)
+	{
+		struct CallerIDOverrideSession *session_p = n->data;
+
+		if (session_p->client != source_p)
+			continue;
+
+		rb_dlinkDelete(n, &callerid_overriding_opers);
+		rb_free(session_p);
+	}
+}
+
 static mapi_hfn_list_av1 um_callerid_hfnlist[] = {
+	{ "umode_changed", check_umode_change },
+	{ "priv_change", check_priv_change },
 	{ "invite", h_hdl_invite },
 	{ "privmsg_user", h_hdl_privmsg_user },
+	{ "client_exit", handle_client_exit },
 	{ NULL, NULL }
 };
 
+static int
+um_callerid_modinit(void)
+{
+	rb_dlink_node *ptr;
+
+	user_modes['g'] = find_umode_slot();
+	if (!user_modes['g'])
+	{
+		ierror("um_callerid: unable to allocate usermode slot for +g; unloading module.");
+		return -1;
+	}
+
+	user_modes['G'] = find_umode_slot();
+	if (!user_modes['G'])
+	{
+		user_modes['g'] = 0;
+
+		ierror("um_callerid: unable to allocate usermode slot for +G; unloading module.");
+		return -1;
+	}
+
+	user_modes['M'] = find_umode_slot();
+	if (!user_modes['M'])
+	{
+		user_modes['g'] = 0;
+		user_modes['G'] = 0;
+
+		ierror("um_callerid: unable to allocate usermode slot for +M; unloading module.");
+		return -1;
+	}
+
+	construct_umodebuf();
+
+	add_isupport("CALLERID", isupport_umode, "g");
+
+	RB_DLINK_FOREACH(ptr, lclient_list.head)
+	{
+		struct Client *client_p = ptr->data;
+		if (IsPerson(client_p) && (client_p->umodes & user_modes['M']))
+			update_session_deadline(client_p);
+	}
+
+	expire_callerid_override_deadlines_ev = rb_event_add("expire_callerid_override_deadlines", expire_callerid_override_deadlines, NULL, 60);
+
+	return 0;
+}
+
+static void
+um_callerid_moddeinit(void)
+{
+	user_modes['g'] = 0;
+	user_modes['G'] = 0;
+	user_modes['M'] = 0;
+	construct_umodebuf();
+
+	delete_isupport("CALLERID");
+
+	rb_event_delete(expire_callerid_override_deadlines_ev);
+}
+
 DECLARE_MODULE_AV2(um_callerid, um_callerid_modinit, um_callerid_moddeinit,
 		   NULL, NULL, um_callerid_hfnlist, NULL, NULL, um_callerid_desc);