Hi, I've followed you very useful command and found a field that represent the user full name (base name + domain) even when active directory is unreachable. the field is kODAttributeTypeAltSecurityIdentities and I can definitely recommend using it to extract domain name.
		NSError *err;
		
		ODNode * searchNode = [ODNode nodeWithSession:[ODSession defaultSession] name:@"/Search" error:&err];
		if (err) {
				writeLog(LOG_ERROR, "error getting Search node : %s", [[err description] UTF8String]);
				return L"";
		}
		
		ODRecord *record = [searchNode recordWithRecordType:kODRecordTypeUsers
																									 name:username
																						 attributes:nil error:&err];
		if (!record) {
				writeLog(LOG_ERROR, "error: couldn't find user %S in Search node : %s", username.c_str(), [[err description] UTF8String]);
				return L"";
		}
		ODQuery *query = [[ODQuery alloc] initWithNode:searchNode
																		forRecordTypes:kODRecordTypeUsers
																				 attribute:kODAttributeTypeRecordName
																				 matchType:kODMatchEqualTo
																			 queryValues:username
																	returnAttributes:@[kODAttributeTypeAltSecurityIdentities]
																		maximumResults:10
																						 error:&err];
		
		NSArray* results = [query resultsAllowingPartial:NO error:&err];
		for(ODRecord *record in results) {
				NSString * domainName = (NSString *)[record valuesForAttribute:kODAttributeTypeAltSecurityIdentities error:nil][0];
				if (domainName != nil) {
						return [[domainName componentsSeparatedByString: @":"] lastObject];
				}
		}
