Customers on Dedicated IPs are able to set up additional branding within the Marketo sending infrastructure. You are able to set up a branded 'envelope_from' so the From Domain used by the Marketo sending servers is associated with your brand instead of with Marketo.
This enables you to further isolate your sending reputation to your own brand and email activity. This can improve delivery rates to email networks looking for this level of alignment (generally smaller B2B domains but this can also help with AOL and Gmail). Branded 'envelope_from' is also key for authentication using DMARC, as it will allow you to align the domains in your email headers.
Marketo's default return path/envelope_from domains include:
San Jose datacenter - @em-sj-77.mktomail.com
London datacenter - @eu-lon-188.mktomail.com
Ashburn datacenter - @potomac1050.mktomail.com
Sydney datacenter - @snsmtp.mktomail.com
To implement this, you will need to chose a sub-domain of your choice for this branding, and set up 3 DNS entries:
The subdomain must be unique. You cannot use your landing page or tracking link domains for your branded return path. Once that DNS setup is completed, submit a case to Marketo Support with those details and we can complete the process by implementing that branding for your instance's emails.