diff --git a/src/mail.js b/src/mail.js
index d2ff27671..cf2fe76cd 100644
--- a/src/mail.js
+++ b/src/mail.js
@@ -1024,9 +1024,11 @@ function sendTestMail(domain, to, callback) {
     getDomain(domain, function (error, result) {
         if (error) return callback(error);
 
-        mailer.sendTestMail(result.domain, to);
+        mailer.sendTestMail(result.domain, to, function (error) {
+            if (error) return callback(new MailError(MailError.EXTERNAL_ERROR, error.message));
 
-        callback();
+            callback();
+        });
     });
 }
 
diff --git a/src/mailer.js b/src/mailer.js
index 19b6a61f9..fcda14a01 100644
--- a/src/mailer.js
+++ b/src/mailer.js
@@ -423,9 +423,10 @@ function oomEvent(mailTo, program, event) {
     });
 }
 
-function sendTestMail(domain, email) {
+function sendTestMail(domain, email, callback) {
     assert.strictEqual(typeof domain, 'string');
     assert.strictEqual(typeof email, 'string');
+    assert.strictEqual(typeof callback, 'function');
 
     getMailConfig(function (error, mailConfig) {
         if (error) return debug('Error getting mail details:', error);
@@ -437,6 +438,6 @@ function sendTestMail(domain, email) {
             text: render('test.ejs', { cloudronName: mailConfig.cloudronName, format: 'text'})
         };
 
-        sendMail(mailOptions);
+        sendMail(mailOptions, callback);
     });
 }
diff --git a/src/routes/mail.js b/src/routes/mail.js
index 019209d59..0075bb5dd 100644
--- a/src/routes/mail.js
+++ b/src/routes/mail.js
@@ -204,6 +204,7 @@ function sendTestMail(req, res, next) {
 
     mail.sendTestMail(req.params.domain, req.body.to, function (error) {
         if (error && error.reason === MailError.NOT_FOUND) return next(new HttpError(404, error.message));
+        if (error && error.reason === MailError.EXTERNAL_ERROR) return next(new HttpError(424, error.message));
         if (error) return next(new HttpError(500, error));
 
         next(new HttpSuccess(202));