De-Duplication in Marketo
By default, Marketo will dedupe new records by email address. If there already is a record in Marketo with the same email address, that record will be updated with the new information. If no matching email is found, a new record is created.
If you set up a custom dupe rule, Marketo will match on email as primary key, and another field as a secondary key. For example, if you add Last Name as a secondary dupe field, Joe Smith (email@example.com) will create a new record, even though Catherine Doe with the same email address is already in the database. This is because both email address and last name need to match to update the existing record. So if Joseph Smith (firstname.lastname@example.org) is entered, the first name will be changed from Joe to Joseph, because both email and last name match.
Custom dupe rules apply to list uploads, form submissions and to most API calls. It does not apply to the native CRM sync, which matches on CRM ID instead of email.
Custom dupe rules are typically used for a limited number of scenarios.
Dupe by Lead Partition
The most common scenario is if the Marketo instance has multiple partitions that need to be independent from each other. Normally, the same Lead can exist in only one partition, not in multiple. However, when you add “Lead Partition” as a custom dupe rule, a record with the same email address can exist in multiple partitions. This can be useful if two completely separate business units are on the same Marketo instance.
Dupe by First Name
If multiple members of a household use the same email address, dupe by first name ensures that all members get their own record in Marketo. However, if multiple household members are part of the same email send, only 1 email will be sent (to the first created record). Trigger emails can be sent to both records individually. Communication Limits apply to each record separately, so with a limit of 5 emails and 2 records with the same email address, the email address can receive up to 10 emails per week. If someone uses multiple variations of the first name (e.g. Beth & Elizabeth), this creates unintentional duplicates.
Dupe by Last Name
Dupe by Email and Last Name is often used if multiple employees of the same company use the same email address. The same caveats as for “first name” apply. Also, it is less and less common that people don’t have their own email address.
Dupe by Foreign Lead Key
Some companies maintain their own unique lead key, which allows multiple records with the same email address. To be able to replicate this in Marketo, this lead key can be added as a custom dupe field. However, all form submissions and list uploads will also need to include this Lead Key, otherwise additional duplicates are created. This scenario is therefore often not advisable.