Exhibit 3.23

CERTIFICATE OF FORMATION

OF

ENVOY LLC

This Certificate of Formation of Envoy LLC (the “Limited Liability Company”), dated October 27, 2006, is being duly executed and filed by Charles A. Mele, as an authorized person to form a limited liability company under the Delaware Limited Liability Company Act (6 Del. C. §18-201 et seq.) (the “DLLCA”).

The undersigned, being duly authorized to execute this Certificate of Formation, hereby certifies that:

FIRST: The name of the Limited Liability Company is Envoy LLC.

SECOND: The address of the registered office and the name and the address of the registered agent of the Limited Liability Company required to be maintained by Section 18-104 of the Delaware Limited Liability Company Act is The Corporation Trust Company, 1209 Orange Street, Wilmington, New Castle County, Delaware 19801.

THIRD: The Limited Liability Company reserves the right to amend its Certificate of Formation from time to time in accordance with the DLLCA.

FOURTH: The initial Limited Liability Company Agreement of the Company (the “LLC Agreement”) shall be adopted by its sole member. The LLC Agreement may contain any provision for the regulation and management of the affairs of the Limited Liability Company not inconsistent with law or this Certificate of Formation,

State of Delaware

Secretary of State

Division of Corporations

Delivered 12:50 PM 10/27/2006

FILED 12:50 PM 10/27/2006

SRV 060988824—3163775 FILE

IN WITNESS WHEREOF, the undersigned has duly executed this Certificate of Formation as of the day and year first written above,

/s/ Charles A. Mele

Charles A. Mele

Authorized Person