dedup if new record gets created in Marketo, but already exists in SFDC

[Anonymous]

Is it possible to NOT create a new record in Marketo if it already exists in SFDC? My guess is there's no way since it won't be able to dedup the record since it doesn't exist in Marketo. Instead it will create a duplicate SFDC record that already exists correct?
What is best practices for mitigating duplication of leads and contacts between Salesforce and Marketo?

[Adam_Vavrek1]

It is possible - if the email address in Marketo matches the email address in Salesforce. If this is the case, Marketo will update the other fields that are in SFDC. If the email addresses are different, a new record will be created in SFDC. Are you familiar with the Possible Duplicates Smart List in the Lead Database?

[Kristen_Malkov1]

What types of duplicates are you seeing? Depending on the fields that are causing duplicates to occur you could block updates from the admin side for the sync. 

Generally, I use CRM fusion to alleviate this problem and merge the records. This generally alleviates duplicate issues if it's based on the email address field missing, like Adam mentioned above.

[Josh_Hill13]

The best way to mitigate duplicates is to sync ALL records betweeen the systems.

Marketo cannot dedupe emails againts records it doesn't know about. Is there some reason these leads aren't in Marketo?

Records created in SFDC are also NOT deduped.

[Edward_Masson]

Marketo is set up to accept duplicate records from your CRM. Must make sure no reps can create new records without some process in place first to reduce potential dupes
.
As Adam and Kristen have pointed out, Marketo will update/append existing records by their recent modification time stamp. Also, If you have a proces where by you need to push Contacts to a queue in SFDC, then Marketo can create a duplicate lead record in SFDC because Contacts can't be in Lead queues (SFDC functionallity).

Some things to be aware of.