"Delivery of a copy" within this Rule means handing it to the attorney or to the party; or leaving it at the attorney's office with a clerk or other person in charge thereof; or, if there is no one in charge, leaving it in a conspicuous place therein; or, if the office is closed or the person to be served has no office, leaving it at the dwelling or usual place of abode with some person of suitable age and discretion then residing therein. Service by mail or electronic mail is complete upon mailing, unless an electronic response is received indicating that the electronic mail is undeliverable, in which case an alternative method of service shall be used, including repeat service by electronic mail until there is no electronic response indicating that the mail is undeliverable.
Del. Fam. Ct. R. Civ. P. 5