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Features

SMTP setup with Mailtrap

Connect Mailtrap as an SMTP relay to the Application Platform – step by step.

On this page

This guide walks through setting up an SMTP account with Mailtrap and entering the values into the Application Platform. Mailtrap offers two products: Email Sending for real delivery (which we set up here) and an Email Sandbox for safe testing.

Overview diagram

The delivery path: your application uses the SMTP credential stored on the platform and talks to Mailtrap; Mailtrap delivers the message to the recipient’s domain.

flowchart LR
  subgraph platform["Application Platform"]
    cred["Organization SMTP credential"]
  end
  subgraph app["Project backend"]
    svc["Outbound mail"]
  end
  subgraph mailtrap["Mailtrap"]
    relay["SMTP relay (Email Sending)"]
  end
  subgraph dest["Recipient"]
    mx["Recipient mail server"]
  end
  svc -->|"reads config"| cred
  svc -->|"TLS, port 587"| relay
  relay --> mx

Steps in Mailtrap

  1. Create or open your account at mailtrap.io and sign in.
  2. Add a sending domain: enter your sender domain under Sending Domains. Mailtrap shows you the DNS records (SPF, DKIM, DMARC) to set at your domain provider – sending is only enabled after verification.
  3. Get the SMTP credentials: open Integration → SMTP for the verified domain. Mailtrap shows you host, port, username, and the API token used as the password.
  4. Optional: send a test email to verify the setup.

Entry in the Application Platform

Create a new SMTP credential under Email delivery and enter the values from the Mailtrap integration page:

Platform field Value at Mailtrap (Email Sending)
SMTP host live.smtp.mailtrap.io
SMTP port 587 (STARTTLS)
SMTP user api
SMTP password Your Mailtrap API token
Sender address An address of your verified sending domain
Sender name Display name for recipients

Save – your projects can then use the credential for sending.

Warning
Don’t confuse these credentials with the Email Sandbox (sandbox.smtp.mailtrap.io): the sandbox never delivers to real recipients but catches mails in a test inbox. For production sending you need the values from Email Sending.

Tip: sandbox for testing

For development and staging you can create a second SMTP credential with the sandbox credentials: all mails then land in the Mailtrap test inbox instead of reaching real recipients – including HTML and spam checks.

Troubleshooting

  • Authentication failed: the username must be api, the password is the API token – check that it was copied completely.
  • Sending rejected / not delivered: sending domain not verified yet – check the DNS records (SPF/DKIM/DMARC) under Sending Domains.
  • Mails end up in the test inbox: you are accidentally using the sandbox credentials instead of Email Sending.

See also