email campaign - multiple profiles with the same email address

When multiple users with matching emails are all in-segment to receive a campaign, a random user profile with that email address is chosen at the time of sending. This way, email is only sent once and is "deduped" which ensures that it doesn't reach the same email multiple times. Note that this deduplication occurs if the users targeted are included in the same dispatch. Therefore triggered campaigns may result in multiple sends to the same email address (even within a time period where users could be excluded due to re-eligibility) if different users with matching emails perform the trigger event at different times.

Multiple message variants: in a multi-variant campaign, if multiple users with the same email address are included in a scheduled send, the sends will be deduped at the time of sending if they are in the same dispatch even if the users are assigned to different message variations.

Canvases: Users are not deduped by email on canvas entry, so it is possible that users are not deduped beyond the first step of a canvas if they are progressing at slightly different times due to rate limited entry or another factor.

Exception (sort of): API Triggered Campaigns: API-triggered campaigns will dedupe or send dupes depending on where the audience is defined. In short, the duplicate emails have to be directly targeted as separate User_ids within the call in order to receive multiple details. Below are three possible scenarios for API-triggered campaigns.

Scenario 1: Duplicate Emails in target segment - Deduped: If the same email appears in multiple user profiles that are grouped together in the dashboard's audience filters for an API-triggered campaign, only 1 of the profiles will get the email.

Scenario 2: Duplicate emails in Different User Ids within recipients object - Dupe Sends: If the same email appears within multiple External_user_IDs referenced by the recipient's object, the email will be sent twice.

Scenario 3: Duplicate emails due to duplicate User Ids within Recipients object - Deduped: If you try to add the same user profile twice, it does dedupe.