In email-to case, duplicate cases are created when the email is sent/cc'd several addresses (cc).
When I send an email to the email-to-case address AND to another person (in the cc of the mail), it creates 3 cases in Salesforce. (I don't know why 3... and the 3rd one is created several minutes after the first 2).
If I send an email only to the email-to-case address, it creates only one case.
Do you know how I can avoid this duplicate case?
* EDIT *
After some other tests, I see that some cases without cc are also created with duplicate... so it is not not the reason of the problem.
I tested to use the big email adress of the email to case (the normal email adress of the email to case redirect to this big email adress) and then I havn't the duplicate problem.