Whitelisting Emails Specific to Your Instance

A document by KCS Integration on behalf of Roxann McGlumphy on Oct 24, 2017Last modified by Vishal Sharma on Jun 26, 2018
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Issue Description
You or your customer have a global block on emails sent from servers with the domain "mktomail.com." You would like to keep the global block but allow email from your own Marketo instance to pass through.


Issue Resolution
The return-path (or envelope_from) in the header of most Marketo emails includes the domain "mktomail.com." Some email servers may have a global block on this domain which prevents delivery of your Marketo emails. There are two options for bypassing this global block.


  • Contact your account manager to see about added the Branded Envelope_From feature to your instance. This will replace the "mktomail.com" domain with a domain of your choice.
  • Have the email admin whitelist a Regex version of your return-path/envelope_from.  Which Regex you use will depend on which datacenter houses your instance.
    1. To determine the datacenter, look at the URL for your Marketo instance and see which letters come after the "https://app-". "SJ" is for San Jose, "AB" is Ashburn, "E" is London, and "SN is Sydney
    2. The Regex you will use is as follows:
    3. Replace "munchkin_id" with the Munchkin ID for your Marketo instance. This operates as the unique identifier to allow only email from your Marketo through the block. Other email from the "mktomail.com" domain will still be blocked.

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