Saying that as part of the Duaa to the dead in a graveyard is sunnah.
However, such greetings to shrines and Darghas are not permissible as people commit shirk by seeking their assistance and refuge.

sheikh as the meaning of assalamu alaikum means may peace be upon you so can I send salaam to aliwalias mazar while crossing it or going that way….can I also send salaam while crossing a graveyard? Is it a shirk activity if yes then why

Shirk and its different forms | August 21, 2017 5:47 pm
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Sheikh in my local masjid the imam n people seek help from Others ,other than Allah n stand up to send Salam upon Beloved prophet.shall i pray behind that iman or change masjid
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there was a frame on a wall of a hall and on it was written ya Allah ya muhammad (pbuh) which didnt belong to me but i removed it from the wall and put it in different room without telling them i knew tht these types of things should be destroyed but i just removed it and put in different room unhanged on one side and i didnt realised that i should burn it now wht should i do? at my relative’s place