- Log in to your account at 123-reg.co.uk.
- Choose the domain you wish to use with Google Apps in the Manage Domains drop-down box, and click Modify Domain.
- Choose the fifth option - Manage DNS.
- Include the MX record values shown in the MX record values table.
- Click Update DNS.
Be aware it may take as long as 72 hours before DNS changes are propagated, depending on the time to live (TTL) that was configured for your records. Until records have been updated worldwide, you will still receive traffic to your old server.
Follow the steps within Troubleshoot MX records to fix your DNS setup.