I'm part of Marketo's Privacy Team, and I evaluate applications for Trusted IPs and help manage this program.
Trusted IPs are shared IPs for low volume customers who certify their email sending practices with us to be in line with best practices. Additionally, Trusted IP customers cannot cause abuse reports or blacklist issues, or other deliverability problems. (If a customer on these IPs causes an issue, they are removed.)
Dedicated IPs require a certain minimum volume to be effective. Email reputation is sort of like a credit score, where no credit = bad credit. With email, you must send a certain volume for the reputation systems to remember you and give you the benefits of being a good sender. Otherwise, you will be treated as though you are a new sender every time, which means you will be subjected to additional antispam measures. Sending from a dedicated IP without the volume to support it can result in worse deliverability than sending from our standard shared IPs. Our current minimum volume threshold for a dedicated IP is 100k/mo.
We wanted to give customers who don't send enough mail to qualify for a dedicated IP another option besides our standard shared IPs. We still believe our standard shared IPs provide good deliverability and we work hard to maintain it. That said, it can be nice to send with a small group of other low volume senders who are all very committed to being good email citizens.
Trusted IP customers meet the following criteria:
*must send with Marketo shared IPs at least 3 months
*send below ~75k/mo
*no abuse reports or blacklist incidents (for at least 1 year - older customers who have had issues far in the past can qualify)
*careful opt-in process for data acquisition
*general good reputation online, not associated with spam
I hope this helps explain this option! Customers interested in joining our Trusted IPs should contact Marketo Support for an evaluation form. Once you complete the form, Support will escalate this to the Privacy Team and we will complete the evaluation. If for any reason you are not approved, we will let you know why and work with you to recommend changes if you wish to reapply in the future.