I have a situation where the new Transactional Messaging API is used for sending high priority emails. However, the system that triggers this does not have the SubscriberKey available that we normally use in SFMC so the email address is used as value for the contactKey attribute in the payload. Now I thought that by selecting "Only update existing subscribers" this would mean no entry would be made in the All Subscribers list and I wouldn't need to put a process in place to clean up but I'm reading conflicting answers online. Can anyone tell me definitively if this is correct? So no need to put a deletion proces in place? Note I am not using a legacy triggered send, it's the new transactional email API. enter image description here

1 Answer 1


To send an email, the subscriber has to be on the All Subs list. So it will create a new contact to send to them

Be forewarned when you delete contacts they first are suppressed and can not be sent to till they are completely deleted, So if you are deleting a large amount and have large # of sendable DE's the process can take awhile

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