On 09-03 we exportet all our leads from Marketo. We exportet the ID Field and the Email-Field. When we use these ID's to trigger campaings via our website, Marketo sometime says that some ID's dont exist. When we search in marketo on email-adres we find out that the leads suddendly have a different Lead ID.
Does anyone know why this happens en what we can do to stop it.
Lead ID never changes. However, it is possible that you have multiple records with the same email address and different Lead IDs. Also, if you merge records, only 1 of the Lead IDs will remain. Also, it is possible that something is wrong with the API call that you're making.
In any case, it's probably best to open a support case and provide specifics, such as a specific email address and Lead ID, plus the exact API call request and response. Without that info, it will be impossible to determine the cause of the issue you're experiencing.