Troubleshooting

This page covers common issues you might encounter when using Email Sandbox and their solutions.

Connection errors

If you can't connect to the Sandbox SMTP server and receive errors like Connection cannot be established or Connection timed out, follow these troubleshooting steps:

1

Test your connection using the Telnet utility

Terminal

telnet sandbox.smtp.mailtrap.io 2525

If Telnet shows that a connection can't be established with our server, you should:

2

Try alternative SMTP ports

Use another SMTP port, such as 2525, 465, or 25.

In most cases, connection issues are related to the firewall blocking the SMTP port.

3

If none of these ports work, try connecting with:

• A different machine

• A different location

• A different ISP

• A VPN connection

This will help identify the route affected by the issue.

4

Check idle timeout

If you've opened an SMTP connection and haven't closed it afterward, the SMTP server will close the session after the idle timeout time.

5

Verify server status

To make sure our SMTP server is up and running, go to the Status page. Here, you can check the SMTP server availability from different locations.

If the issue persists after trying all these steps, please contact us at [email protected].

Authentication error (530)

Error message:

Expected response code 250 but got code "530", with the message "530 5.7.1 Authentication required"

When you receive the 5.7.1 Authentication required error, it means that either:

• The SMTP authentication is disabled in your configuration, or

• The authentication failed

In either case, an email was not sent.

Solution:

1. Enable SMTP authentication in your settings

2. Configure your app to enable SMTP authentication

3. If it is already enabled, revise your credentials and authentication settings

4. Try sending an email again

Messages not delivered to Sandbox

If your messages aren't appearing in your sandbox, follow these troubleshooting steps:

1

Verify your SMTP integration is correct

1. Go to your sandbox Integration tab

2. Compare hostname, username, and password with those in your app

If you reset SMTP/POP3 credentials, all existing integrations are affected and must be updated.

2

Verify limits

Make sure that the number and frequency of the messages sent correspond to the terms of your billing plan. Check:

• Rate limits (emails per 10 seconds)

• Monthly message limits

• Email size limits

3

Check SMTP logs

View your SMTP logs and check whether you received any errors. To view SMTP logs, enable debugging in your email code.

For example, see how to enable debugging in PHPMailer.

4

Contact support

If you still can't figure out why your emails aren't getting delivered to your sandbox:

1. Save an undelivered message in .eml format

2. Remove any sensitive information

3. Send it to us at [email protected]

Sandbox email address disabled

Email per sandbox is a premium feature available in the Basic, Team, Enterprise, or Business plans.

Enabling after upgrade

Once you upgrade your plan, make sure you activate the address:

1

Go to the Email Address tab in your sandbox.

2

Click the three-dot menu to the right, and select Enable.

Alternative: SMTP integration

You can freely test emails without this feature. With any plan (including the free tier), you can integrate SMTP credentials into your app and receive every email this way.

You'll find the integration samples for over 20 frameworks and libraries on the Integration page of your sandbox. You can also use the API without any restrictions.

Tech info / headers unavailable

The Tech Info tab will show the following headers if they're present in an email:

• Message_id

• X_mailer

• Sender

• From

• To

• Cc

• Reply_to

• Return_path

If any of these headers haven't been specified (for example, an email doesn't have a reply_to header specified), it won't be displayed.

BCC Header

If you are on the Business plan or higher (view plans), you will also see the BCC header in this tab (if specified for the message).

On lower plans, no BCC field will appear even if it was included in a message.

Team members limit reached

If you can't add more team members, you may have reached the user limit of your plan.

Solution: Upgrade your plan to increase the team member limit. Check pricing plans for details.

Automatic forwarding issues

If your test emails aren't being forwarded automatically, there's very probably an error in the auto-forwarding configuration.

How auto-forwarding works

When auto-forwarding to predefined addresses/domains, sandbox verifies the TO and CC headers of a message (BCC is ignored).

An email is forwarded if:

• TO or CC of your email matches the value in the Emails list, OR

• The domain in the TO or CC of your email matches the value in the Domains list

A forwarding rule needs to be verified (its status must be Active) before it can be considered. To do that, you'll need to confirm the email address or the domain's ownership.

Troubleshooting steps

If a particular email is not forwarded:

1. Check its headers via the Tech Info tab

2. Verify you have the correct TO or CC address set

3. Ensure your forwarding rule status is Active

4. Confirm the email address or domain has been verified

Furher reading: Automatic Email Forwarding

Suspicious emails in sandbox

If you see emails in your sandbox that you didn't send from your app, someone may have accessed your SMTP credentials.

If you suspect unauthorized access to your sandbox, reset your credentials immediately.

How to reset credentials

Don't panic — it's very easy to reset your credentials:

1

Log in to your dashboard, open your sandbox, and go to the Integration tab.

2

Click the Reset Credentials button, and your details will be reset right away.

3

Make sure you update the credentials in your app, as old credentials will no longer be valid.

We don't store information about the server or IP address that sent messages. As such, we won't be able to help you track down the sender.

Related articles

• How to integrate Email Sandbox with your application

• Features and Limits

• Automatic Email Forwarding

• Email Sandbox FAQs

Need More Help?

If you don't find the solution to your problem here, contact our support at [email protected].