If a custom trigger is created and used, it will always match to a contact or lead based on the fields crmId, emailaddress or telephone. As custom triggers are supposed to get actions easily by other systems (for example website to crm), it would be great if custom matching strategies could be implemented. Through this, the information which is already available at the other system (for example some kind of id from this system) could be used to find the right contact/lead in the crm.