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Google Workspace host routes do not support username and password authentication. Contact mySMTP support to arrange IP-based authorization.

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Before you start

Have these details ready:
Use the exact relay hostname from your setup email. relayxx.mysmtp.com is only an example.

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Add mySMTP as a host route

1

Open the Admin console

Go to the Google Admin console and sign in with a Super Admin account.
2

Go to Gmail hosts

Navigate to Apps > Google Workspace > Gmail > Hosts.
3

Add a new host

  1. Click Add route or Configure.
  2. Enter a name such as mySMTP.
  3. Under Specify email server, enter your relay hostname (e.g. relayxx.mysmtp.com).
  4. Set Port to 587.
  5. Select Require TLS connection.
  6. Click Save.

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Apply the route to outbound mail

1

Open Gmail routing

In the Admin console, go to Apps > Google Workspace > Gmail > Routing.
2

Create an outbound gateway rule

  1. Scroll to Outbound and click Configure or Add another rule.
  2. Give the rule a name such as Route via mySMTP.
  3. Under For the above types of messages, do the following, select Change route.
  4. Choose the mySMTP host route you created.
  5. Click Save.
Google Workspace host routes do not support username and password authentication to an external SMTP host. Authentication is handled by the sending IP address. Contact mySMTP support to authorize Google Workspace’s outbound IP ranges for your account.

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SPF record

Add both Google Workspace and mySMTP to your domain’s SPF record. A typical record looks like:
If you already have an SPF record, add the includes without removing existing entries. Too many DNS lookups can cause SPF failures. Use the Deliverability Toolbox to check your SPF record.

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Test the connection

  1. Send a test email from a Google Workspace mailbox to an external address, such as a Gmail account or your own.
  2. Confirm the message arrives. In the received message headers you should see it passed through your mySMTP relay.
  3. If the message does not arrive, check the Email log search in the Admin console under Reports > Email log search.

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Troubleshooting

  • Messages still go through Google directly: Make sure the routing rule is enabled and applies to outbound mail. Check that no other routing rule with a higher priority overrides it.
  • TLS connection fails: Confirm the host route requires TLS and that your network allows outbound connections on port 587.
  • Relay access denied: Verify that mySMTP support has authorized Google Workspace’s outbound IP ranges for your account.
For more error codes, see Common SMTP errors.