diff --git a/src/agents/collector/CMakeLists.txt b/src/agents/collector/CMakeLists.txt
index e180ab1..963a1a8 100644
--- a/src/agents/collector/CMakeLists.txt
+++ b/src/agents/collector/CMakeLists.txt
@@ -16,6 +16,7 @@ add_custom_command(
 add_executable(bongocollector
 	collector.c
 	external_accounts.c
+	external_store.c
 	${EXTERNAL_ACCOUNTS_SQL_C}
 )
 
diff --git a/src/agents/collector/external_store.c b/src/agents/collector/external_store.c
new file mode 100644
index 0000000..c7c9d99
--- /dev/null
+++ b/src/agents/collector/external_store.c
@@ -0,0 +1,88 @@
+#include <config.h>
+
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <xpl.h>
+#include <memmgr.h>
+#include <bongoutil.h>
+#include <bongoagent.h>
+#include <nmap.h>
+#include <nmlib.h>
+#include <msgapi.h>
+#include <connio.h>
+#include <bongostore.h>
+
+#include "external_store.h"
+
+static int
+SafeNmapToken(const char *value)
+{
+    return value != NULL && value[0] != '\0' &&
+           strpbrk(value, "\r\n\"\\") == NULL;
+}
+
+static void
+SetError(char *error, size_t error_size, const char *message)
+{
+    if (error != NULL && error_size > 0) {
+        snprintf(error, error_size, "%s", message != NULL ? message : "unknown error");
+    }
+}
+
+int
+CollectorStoreSubmitFile(const char *owner, const char *folder,
+                         FILE *message, size_t message_size,
+                         time_t received_at, char *error,
+                         size_t error_size)
+{
+    struct sockaddr_in store_address;
+    Connection *connection = NULL;
+    char response[CONN_BUFSIZE + 1];
+    int result = -1;
+
+    if (!SafeNmapToken(owner) || !SafeNmapToken(folder) || message == NULL ||
+        message_size == 0 || message_size > INT_MAX) {
+        SetError(error, error_size, "invalid external message submission parameters");
+        return -1;
+    }
+    if (MsgAuthGetUserStore(owner, &store_address) != 0) {
+        SetError(error, error_size, "cannot locate the user's Bongo store");
+        return -1;
+    }
+    connection = NMAPConnect(NULL, &store_address);
+    if (connection == NULL) {
+        SetError(error, error_size, "cannot connect to the user's Bongo store");
+        return -1;
+    }
+    if (!NMAPAuthenticateThenUserAndStore(connection, (unsigned char *) owner)) {
+        SetError(error, error_size, "cannot authenticate to the user's Bongo store");
+        goto done;
+    }
+    if (NMAPRunCommandF(connection, response, sizeof(response),
+                        "WRITE \"/mail/%s\" %u %zu T%lu\r\n", folder,
+                        STORE_DOCTYPE_MAIL, message_size,
+                        (unsigned long) received_at) != 2002) {
+        SetError(error, error_size, "the Bongo store rejected the target folder");
+        goto done;
+    }
+    rewind(message);
+    if (ConnWriteFromFile(connection, message, (int) message_size) != (int) message_size ||
+        ConnFlush(connection) < 0) {
+        SetError(error, error_size, "cannot send the external message to the Bongo store");
+        goto done;
+    }
+    if (NMAPReadAnswer(connection, response, sizeof(response), TRUE) != 1000) {
+        SetError(error, error_size, "the Bongo store could not import the external message");
+        goto done;
+    }
+    SetError(error, error_size, "");
+    result = 0;
+
+done:
+    NMAPQuit(connection);
+    ConnFree(connection);
+    return result;
+}
diff --git a/src/agents/collector/external_store.h b/src/agents/collector/external_store.h
new file mode 100644
index 0000000..5cd9ee6
--- /dev/null
+++ b/src/agents/collector/external_store.h
@@ -0,0 +1,13 @@
+#ifndef BONGO_COLLECTOR_EXTERNAL_STORE_H
+#define BONGO_COLLECTOR_EXTERNAL_STORE_H
+
+#include <stddef.h>
+#include <stdio.h>
+#include <time.h>
+
+int CollectorStoreSubmitFile(const char *owner, const char *folder,
+                             FILE *message, size_t message_size,
+                             time_t received_at, char *error,
+                             size_t error_size);
+
+#endif