To say "YA" (O) with Prophet[A.S],Awliyas[rah] after their death is allowedVIDEO : Ya Rasulallah (SAW) Kehne ka Jawaz aur Ikhlas fil Amal by Dr.Muhammad Tahir ul Qadri
VIDEO : Ibn Taymiyya approves of Ya Muhammad
VIDEO : Mufti Akmal's views on Hazir Nazir and saying Yaa Rasulallah(sallalahu Alaih wa Sallam)
Calling out, Ya Rasool Allah (صلی اللہ علیہ وسلم) (o prophet of allah عزوجل) | Ja-Al Haq
THE VALIDITY OF SAYING YA RASOOLULLAH (Peace be upon him) By Tajul-Ulama Badrul-Fuqaha Mujaddid-e-Mehta-Hadra Imam Ahmad Raza Al-Qadri Barkati Muhaqqiq Barelwi (Radi Allah Unho)
To say "YA" (O) with Prophet[A.S],Awliyas[rah] after their death is allowed
Proclaiming Ya RasoolALLAH in Personal Invocation or as Slogan in an Assembly
YA MOHAMMED : PROOF
VIDEO : Saying YA NABI in Namaaz ( YA NABI SALAAM ALAYK) Dr Tahir ul Qadri
Ya Muhammad صلى الله عليه وسلم