diff --git a/src/agents/collector/collector.c b/src/agents/collector/collector.c
index 0468711..5777f7a 100644
--- a/src/agents/collector/collector.c
+++ b/src/agents/collector/collector.c
@@ -41,6 +41,64 @@
 
 CollectorGlobals Collector = {0};
 
+static size_t DiscardCurlData(char *ptr, size_t size, size_t count, void *data)
+{
+    (void) ptr; (void) data;
+    return size * count;
+}
+
+static int ProbeExternalAccount(sqlite3 *database,
+                                const CollectorExternalAccount *account,
+                                long now)
+{
+    CURL *curl = NULL;
+    char secret[512];
+    char url[768];
+    char error[CURL_ERROR_SIZE] = {0};
+    const char *scheme;
+    CURLcode code;
+    int secretResult;
+
+    if (account->inbound_protocol[0] == '\0' || account->inbound_host[0] == '\0' ||
+        account->inbound_secret_id[0] == '\0') {
+        CollectorAccountsMarkResult(database, account->id, now, 0,
+                                     "external account is missing transport credentials");
+        return -1;
+    }
+    secretResult = CollectorAccountsSecretGet(database, account->inbound_secret_id,
+                                               secret, sizeof(secret));
+    if (secretResult != 1) {
+        CollectorAccountsMarkResult(database, account->id, now, 0,
+                                     "external account secret not found or too long");
+        return -1;
+    }
+    scheme = strcmp(account->inbound_protocol, "imap") == 0 ? "imap" : "pop3";
+    if (snprintf(url, sizeof(url), "%s%s://%s:%d/%s", scheme,
+                 strcmp(account->inbound_tls, "implicit") == 0 ? "s" : "",
+                 account->inbound_host, account->inbound_port,
+                 account->destination_folder[0] != '\0' ? account->destination_folder : "INBOX") >= (int) sizeof(url)) {
+        CollectorAccountsMarkResult(database, account->id, now, 0, "external account URL too long");
+        return -1;
+    }
+    curl = curl_easy_init();
+    if (curl == NULL) return -1;
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+    curl_easy_setopt(curl, CURLOPT_USERNAME, account->inbound_username);
+    curl_easy_setopt(curl, CURLOPT_PASSWORD, secret);
+    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 30L);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 60L);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, DiscardCurlData);
+    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, error);
+    code = curl_easy_perform(curl);
+    curl_easy_cleanup(curl);
+    if (code != CURLE_OK) {
+        CollectorAccountsMarkResult(database, account->id, now, 0,
+                                     error[0] != '\0' ? error : curl_easy_strerror(code));
+        return -1;
+    }
+    return CollectorAccountsMarkResult(database, account->id, now, 1, NULL);
+}
+
 static void 
 CollectorLoop(void *ignored)
 {
@@ -61,6 +119,10 @@ CollectorLoop(void *ignored)
                 Log(LOG_ERROR, "Unable to query due external mail accounts");
             } else if (due > 0) {
                 Log(LOG_DEBUG, "%d external mail account(s) are due for collection", due);
+                CollectorExternalAccount account;
+                if (CollectorAccountsNextDue(accounts, (long) now, &account) == 1) {
+                    ProbeExternalAccount(accounts, &account, (long) now);
+                }
             }
         }
         if (lastCalendarCollection == 0 || now - lastCalendarCollection >= 6 * 60 * 60) {
diff --git a/src/agents/collector/external_accounts.c b/src/agents/collector/external_accounts.c
index 47ba0de..ef64399 100644
--- a/src/agents/collector/external_accounts.c
+++ b/src/agents/collector/external_accounts.c
@@ -82,7 +82,7 @@ CollectorAccountsNextDue(sqlite3 *database, long now,
     sqlite3_stmt *statement = NULL;
     const char query[] =
         "SELECT id, owner, email_address, inbound_protocol, inbound_host, "
-        "inbound_port, inbound_tls, inbound_username, destination_folder, "
+        "inbound_port, inbound_tls, inbound_username, inbound_secret_id, destination_folder, "
         "delete_policy, COALESCE(delete_after_days, 0) "
         "FROM external_accounts WHERE enabled = 1 AND inbound_protocol != 'none' "
         "AND (last_checked_at IS NULL OR last_checked_at + poll_interval <= ?) "
@@ -116,9 +116,10 @@ CollectorAccountsNextDue(sqlite3 *database, long now,
     account->inbound_port = sqlite3_column_int(statement, 5);
     COPY_ACCOUNT_FIELD(6, inbound_tls);
     COPY_ACCOUNT_FIELD(7, inbound_username);
-    COPY_ACCOUNT_FIELD(8, destination_folder);
-    COPY_ACCOUNT_FIELD(9, delete_policy);
-    account->delete_after_days = sqlite3_column_int(statement, 10);
+    COPY_ACCOUNT_FIELD(8, inbound_secret_id);
+    COPY_ACCOUNT_FIELD(9, destination_folder);
+    COPY_ACCOUNT_FIELD(10, delete_policy);
+    account->delete_after_days = sqlite3_column_int(statement, 11);
 #undef COPY_ACCOUNT_FIELD
     sqlite3_finalize(statement);
     return 1;
diff --git a/src/agents/collector/external_accounts.h b/src/agents/collector/external_accounts.h
index 1f2e6d9..2b4cccd 100644
--- a/src/agents/collector/external_accounts.h
+++ b/src/agents/collector/external_accounts.h
@@ -14,6 +14,7 @@ typedef struct {
     int inbound_port;
     char inbound_tls[16];
     char inbound_username[256];
+    char inbound_secret_id[128];
     char destination_folder[256];
     char delete_policy[16];
     int delete_after_days;