Iowa Code § 321.501: Manner of service.

The plaintiff in any action against a nonresident shall cause the original notice of suit to be served by doing all of the following:

1. By filing a copy of the original notice of suit with the director, together with a fee of two dollars.

2. By mailing to the defendant, and to each of the defendants if there are more than one, within ten days after said filing with the director, by restricted certified mail addressed to the defendant at the defendant’s last known residence or place of abode, a notification of the filing with the director.