Hey Kate, Marketo dedupes by email address only by default. I do know that you can add MORE specificity to the deduplication logic, but you can't change away from email address. For example, you can work with Marketo Support (and maybe professional services for a fee as well, I'm not sure if there's a charge associated with this change) to say: dedupe on email address and "region" field.
Out of the box: email address
Possible: email address and "region" field (for example)
Possible: email address and [any other one field you choose]
Not possible: custom field with other unique ID
You can call up Marketo Support, and they'll let you know the process. They will definitely have to escalate the case, and might bring in your Account Rep if there's an increase in cost or a one-time cost associated with this process.
Note: only do this if you really, really, really have to! This will permanently change your Marketo setup, and there will be problems you will never have anticipated now and in the future! I've had clients who had this done years ago, and it makes their lead duplication issue totally colossal—something like 75% of their database became duplicates two years later after their infrastructure changed and Marketo operations people moved elsewhere in the org. I can almost guarantee there's a better way to work within the confines of the email address deduplication without adding this layer (e.g., have you checked out lead partitions which allow separate leads with the same email address, but in a different section of Marketo? That's great for global instances of Marketo, which is one example of this use case.). In most cases, the negative of "email address is our identifier and that's it, full stop" is less than the negative of changing systemic functionality to make this happen.
Cheers,
Edward Unthank | Founder, Etumos
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