The email header in Marketo is fully customizable. It consists of four fields:
To edit these values, click in each field and enter your information.
To set a default From Name and From Email, see Change the Default From Email and From Label.
If you want to use a token, click inside the desired field first, then click the token icon.
You can also make the field dynamic by using segments.
The key icon to the far right in the From Address field lets you know if you’re using a custom DKIM signature.
The counter to the far right in the Subject field helps you keep your subject line below the recommended 50 character limit.
If you exceed 50 characters, the counter turns red to alert you.