O.C.G.A. § 22-2-25 (2019)

(a) Unless service is acknowledged or waived, a copy of the notice of condemnation shall be served by a sheriff or deputy at least 15 days before the day fixed for assessing the damage either:

(1) Personally on the owner of the property or other interest or on the representative of any owner or on any other person entitled to service;

(2) By leaving a copy of the notice at the residence of the owner, representative, or other person entitled to service; or

(3) In the case of an owner, representative, or other person entitled to service who is a nonresident, by mailing a copy to that person’s last known address.

(b) In cases where service cannot be effected by leaving notice at place of residence or by personal service:

(1) Fifteen days before the day fixed for assessing the damages, the sheriff shall post the notice at the door of the courthouse of the county where the property or interest is located; and

(2) One week before the day fixed for assessing the damages, the sheriff shall cause the notice to be published once in the official organ of the county.