diff --git a/.changeset/fix-relay-connect-error.md b/.changeset/fix-relay-connect-error.md
new file mode 100644
index 0000000..a197def
--- /dev/null
+++ b/.changeset/fix-relay-connect-error.md
@@ -0,0 +1,9 @@
+---
+'@maildev/smtp': patch
+'maildev': patch
+---
+
+Fail the relay when the outgoing server cannot be reached. The connection
+error was only logged, so the relay never finished: with auto-relay on, the
+SMTP client sending to MailDev never got its reply, and the manual relay
+request never answered.
diff --git a/packages/smtp/src/__tests__/relay.test.ts b/packages/smtp/src/__tests__/relay.test.ts
index 1e0a2ff..89f1e97 100644
--- a/packages/smtp/src/__tests__/relay.test.ts
+++ b/packages/smtp/src/__tests__/relay.test.ts
@@ -147,6 +147,17 @@ describe('relay raw email stream', () => {
     expect(stream.destroyed).toBe(true)
   })
 
+  it('closes the stream when the outgoing server cannot be reached', async () => {
+    const client = new RelayClient({ host: '127.0.0.1', port: await freePort() }, false)
+    const stream = createReadStream(emlPath)
+
+    const result = await client.relay(email, stream)
+
+    expect(result.success).toBe(false)
+    expect(result.error).toBeInstanceOf(Error)
+    expect(stream.destroyed).toBe(true)
+  })
+
   it('closes the stream when the outgoing server rejects the recipient', async () => {
     const port = await freePort()
     const rejecting = new SMTPServerLib({
diff --git a/packages/smtp/src/relay.ts b/packages/smtp/src/relay.ts
index fcb982e..2cd9f33 100644
--- a/packages/smtp/src/relay.ts
+++ b/packages/smtp/src/relay.ts
@@ -160,8 +160,10 @@ export class RelayClient {
         debug: false,
       })
 
+      // A failed connection is reported here, not through the connect callback
       this.client.on('error', (err: Error) => {
         this.logger.error('SMTP Connection error:', err)
+        reject(err)
       })
 
       this.client.connect((err?: Error) => {