Ala. Code § 11-51-13

In the case of property of an unknown owner or when the sheriff returns “not found” after 10 days as to owners for whom he has a summons, the register or clerk is directed to cause publication to be made for 30 days of the fact of the filing of such tax list, giving a list of the property assessed to owners unknown and to persons for whom a summons has been returned by the sheriff “not found.”