I am configuring my first A/B split test with an email. I know that during a single send to a data extension, normally, Marketing Cloud will dedupe the DE's contents on the email address. However, I'm not sure if this occurs the same way for an A/B split send. My DE contains 130,000 records, including about 50,000 people who appear more than once, with slightly different attributes. I must leave this DE as-is. But I cannot have anyone receiving more than one email out of this send. If the dedupe is performed on each split segment separately, then thousands of subscribers will receive both the A and B versions of the email, and possibly receive the winner a second time.

  • My suspicion is SFMC would only dedupe within each Job - A, B and Remainder. Rather than depend on deduplication at time of send, could you not consider deduping your Sendable DE with a Query before you do the test?
    – Macca
    Commented Jul 7, 2019 at 2:13

1 Answer 1


Answered my own question. After you select a DE, then a deduplicate checkbox appears. But not before. As shown in these screenshots (before/after).

BEFORE: before AFTER: after

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