If you experience problems with Mailtrap, read this article. We explain what to do if you can’t connect to the Mailtrap server, if emails are not delivered as expected, or some features don’t work.

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Connection errors

If you can't connect to the Mailtrap SMTP server, receiving errors " Connection cannot be established" or "Connection timed out", follow the steps described below. 

First, test your connection using the Telnet utility:  telnet 2525 . You can find an example of the successful Telnet output in the Integrations section of any of your inboxes.

If Telnet shows that a connection can't be established with our server, follow the next steps:

  1. Try to use another SMTP port: 2525, 465, or 25. In most cases, the issue is related to the SMTP port being blocked by the firewall.
  2. If none of these ports work, try connecting with a different machine, location, ISP, or use a VPN. This will help identify the route affected by the issue.
  3. Check if the SMTP connection is not closed on idle timeout on the server side. If you opened an SMTP connection and haven't closed it afterward, the SMTP server will close the session after the idle timeout time.

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, please let us know at

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

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.

Please enable SMTP authentication in your settings and configure your app to enable SMTP authentication. If it is already enabled, revise your credentials and authentication settings, and try sending an email again.

Messages are not delivered to my Mailtrap inbox [Mailtrap Email Testing]

If you try sending messages from your app to Mailtrap, but they don't appear in your Mailtrap inbox, first of all, do the following:

1. Check your SMTP integration

  • Go to your inbox SMTP settings 
  • Compare hostname, username, and password with those in your app (if you reset SMTP/POP3, all existing integrations are affected)

2. Make sure that the number and frequency of messages you sent fit the terms of your billing plan.

If everything is correct, then view your SMTP logs and check whether you received any errors. To view SMTP logs, you should enable debugging in your email code. Here is an example of how to make it in PHPMailer

If you still can't find the reason why emails don't arrive at your Mailtrap inbox, please save an undelivered message in .eml format and send it to us at Just don't forget to remove any sensitive information! 

Mail not delivered to the recipient [Mailtrap Email Testing]

Don’t worry, this is expected behavior. 

Mailtrap Email Testing is a fake SMTP server that catches test emails sent from your pre-production environment. It stores each of them in virtual inboxes, making it easy to test them before they’re sent to real users. 

With Mailtrap, you can’t message real recipients. You can, however, test whether emails go out from your project and immediately detect any malfunctions. 

You can also view each message sent this way. To do so, open your Mailtrap dashboard, head to your inbox, and find your emails there. If any of them is missing, your app may have trouble sending emails and it’s something worth looking into.

Read more about how it works in our Getting Started Guide.

Why is my inbox email address disabled? [Mailtrap Email Testing]

Email per inbox is a premium feature that’s not available with the Free, Individual, or Team plans. To activate it, please upgrade to the Business plan or higher ( View the subscription plans). Also, make sure you activate the address. Go to the ‘Email Address’ tab in your inbox, click on the three dots menu to the right, and select ‘Enable’.

Of course, you can freely test emails with Mailtrap Email Testing without this feature. With any plan (including the free tier), you may integrate Mailtrap’s SMTP credentials into your app and receive every email sent this way. You’ll find the integration samples for over 20 frameworks and libraries on your inbox page. You may also use the Mailtrap Testing API without any restrictions. Read more about getting started with Mailtrap.

Email per inbox just opens up some more possibilities. After you enable an individual address for your inbox, you may use it to, for example, capture emails sent from your ESP or any other external service. Each message sent to this address will land in the respective Mailtrap inbox.

Tech info/ headers unavailable? - Sandbox

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.

If you are on the Business plan or higher ( view Mailtrap 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 with a message.

I can’t add more team members

If that happens, you may have reached the user limit of your plan.

Each Mailtrap plan, starting from the Team plan, comes with a maximum number of team members you can add to your projects and inboxes. Free and Individual plans don’t allow adding team members.

For example, if you’re on the Team plan, you have a limit of 20 team members. This means that you can add up to 20 unique users across all your projects and inboxes. This way, if you add, let’s say, to project A and to one of the inboxes under project B, this will count as 2/20 team members.

Of course, a user added to a project will have access to all inboxes under the project. As such, they don't need to be added separately. If you add to project A and then add the same to one of the inboxes under project B, this will count as 1/20 team members.

Please note that the amount of team members is calculated based on users who have already been added plus pending invitations. If your limit is 20, and you have 13 project members and 7 pending invitations, you won’t be able to send a new invitation. First, you’ll need to cancel one of the existing ones or remove one of the invitees.

Automatic Forwarding doesn’t work - Sandbox

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

When auto forwarding to the predefined addresses/domains, Mailtrap verifies the ‘to’ and ‘cc’ headers of a message (bcc is ignored). An email is forwarded if:

  • TO or CC of the email you send match the value in the "Emails" list, or 
  • the domain in TO or CC of the email you send matches the value in the "Domains" list.

Remember that, in order for a forwarding rule to be considered, it needs to be verified (its status must be ‘Active’). To do that, you’ll need to confirm the email address or the ownership of the domain.

If a particular email is not forwarded, check its headers via the Tech Info tab to see whether you have the correct TO or CC address set.

I see suspicious emails in my Mailtrap inbox - Sandbox

Have you received a suspicious message in your Mailtrap inbox and have reason to believe that it wasn’t sent from your app? If so, someone may have got hold of your Mailtrap SMTP credentials.

Don’t panic though. It’s very easy to reset your credentials. Please log in to your Mailtrap dashboard, open your inbox, and go to the ‘SMTP Settings’ tab. There, click the ‘Reset Credentials’ button and your details will be reset right away. Make sure you update them in your app as old credentials won’t be valid anymore.

Unfortunately, we don’t store the information about the server or IP address that sent the message in question. As such, we won’t be able to help you track down the sender.

MS Office 365 threat management - Email API

Sometimes transactional messages from Mailtrap (such as email confirmations, invitations to join an inbox, invoices, etc.) can be sent to Threat management  >> Quarantine by MS Office 365. 

If you have faced this issue, follow these steps to resolve it:

  1. Go to
  2. Select the emails sent from Mailtrap.
  3. Click the Release messages button.
  4. Check the “Add sender to your organization’s allow list” checkbox.

When signing up for Mailtrap, you have an option to use Office 365 account authorization "oAuth" for smooth integration. In this case, email confirmation won't be required. 

Sending from domain is not allowed - Email API

Error: Mail command failed: 550 5.7.1 Sending from domain is not allowed

In case you get this error you tried to send an email using SMTP with Mailtrap Email API.

The possible reasons for getting it are:

  • You send an email with FROM: {anything}, but in Mailtrap your verified The verified domain and FROM: domain in your emails should match.
  • Some DNS records for your domain and now it's not verified. Go to Domains, click on your domain, and check if all DNS records are found by Mailtrap (all should be green).
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