letter of acceptance
After I wrote this post I found this statement in the Maricopa County form for serving a letter of acceptance: I have also enclosed an “Acceptance of Service” form. Sign this form in front of a Notary Public and return it to me in the self-addressed stamped envelope. This does not affect your right to object to or to disagree with the request that has been filed. If you choose to not sign the “Acceptance,” you may be charged for any extra costs required to serve the papers by other means (Arizona Rules of Civil Procedure 4.1(c)). Signing the “Acceptance” will save you the cost of hiring a process server or the sheriff to serve the papers. So if the letter of acceptance isn't signed apparently there are other means of serving the summons.