Duplicate leads when I create a new lead in Marketo and then a new lead comes in through Salesforce

[Anonymous]

My understanding was that Marketo de-dupes based on email address but in this case I'm seeing two leads with the same email address:

When I manually create a lead in Marketo and then create a new lead via our web site (which also creates a new lead in Salesforce) I end up with two leads with the same email address in Marketo. Is there a way to avoid this?

[Josh_Hill13]

Marketo DOES NOT dedupe for leads originating in SFDC. Your external form should stop sending leads to SFDC if it is also sending leads to Marketo.

Also, if you assign a Contact to a Queue, it will create a new lead.