The European order for payment may be served on the defendant in accordance with the national law of the State in which the service is to be effected, by one of the following methods:

1. (a)

   personal service attested by an acknowledgement of receipt, including the date of receipt, which is signed by the defendant;

2. (b)

   personal service attested by a document signed by the competent person who effected the service stating that the defendant has received the document or refused to receive it without any legal justification, and the date of service;

3. (c)

   postal service attested by an acknowledgement of receipt, including the date of receipt, which is signed and returned by the defendant;

4. (d)

   service by electronic means such as fax or e-mail, attested by an acknowledgement of receipt, including the date of receipt, which is signed and returned by the defendant.