It says in Fatawa al-Lajnah al-Daimah:
“Making du’a after the obligatory prayers is not Sunnah if it is done by raising the hands, whether that is done by the imam alone or a member of the congregation alone, or it is done by them both together. Rather that is bid’ah, because it was not narrated that the Prophet (peace and blessings of Allah be upon him) or any of his Companions (may Allah be pleased with them) did that. With regard to making du’a without doing that (raising the hands etc.), there is nothing wrong with it, because there are some ahadith concerning that.” (Fatawa al-Lajnah al-Daimah, 7/103)