(1) An entity's or foreign entity's registered agent shall be its agent for service of process, notice, or demand required or permitted by law to be served on the entity or foreign entity.
(2) If an entity or foreign entity has no registered agent, or the agent cannot with reasonable diligence be served, the entity or foreign entity may be served with process, or any notice or demand may be served by registered or certified mail, return receipt requested, addressed to the entity or foreign entity at its principal office and to the attention of the person or office appropriate for giving notice to the entity or foreign entity. Service shall be perfected under this subsection at the earliest of:
(a) The date the entity or foreign entity receives the mail;
(b) The date shown on the return receipt, if signed on behalf of the entity or foreign entity; or (c) Five (5) days after its deposit in the United States mail, as evidenced by the postmark, if mailed postage paid and correctly addressed.
(3) This section does not prescribe the only means, or necessarily the required means, of serving an entity or foreign entity.