How do I prevent duplicates when importing leads if they are already a Contact?

Question

 

I am importing a list of 10,000 leads.  I am selecting "Matching Type" = email to prevent duplicates.  But I've noticed that some email addresses in the imported database are already contacts.  How do I prevent duplicates of leads that are already contacts?

 

Best Answer

 

Without some third-party-tool, you can't  -> check appexcange for deduplication tools that can perform deduplication on both: contacts&leads.