Log in to DreamHost administrative control panel at https://panel.dreamhost.com/ by entering your email address/Web ID and Web panel password.
Click 'Mail' from the left hand side navigation and select 'MX' from the options.
Click 'Edit' beside the domain name for which the MX records are to be updated.
Delete all existing MX records under 'Custom MX Records'.
In the first four text boxes, enter:
Click 'Update your custom MX records now!'
The MX records for your domain are updated now. But it may take up to 48 hours for the changes to take effect.