Agent question Living abroad, no mail received

[Happytime 0]

I am a USC living abroad with my wife, like many in our position, we have been fortunate enough to be speedily moving through the process. However we have received NO mail at our address (we are in Vietnam and the government post here is really bad). The question is, if we are not getting mail is it better to appoint my mother (who lives in America and will be co-sponsoring my wife) an "agent" so that at least someone will be getting mail? After reading this it sounds as though my mother could concievably send all the supporting documents from her home in America, is this true? we have previously sent all docs from abroad (which expidited the process) should we continue to do that? very confused.