We've had an issue recently where our networking team updated our SPF setup by switching include:mktomail.com to ip4:#.#.#.#. We had hit 11 lookups due to using Office 365, Salesforce and other vendors. The change was perfectly valid since we have a dedicated IP but we still received an alert from Marketo that our SPF was misconfigured. It seems that Marketo does a string match for include:mktomail.com and that is all. I'd like to propose that the SPF validation done by Marketo also checks for the dedicated IP that an instance has. This way we would be able to limit our number of increasing SPF lookups.
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