That Islamic stamp sounds like Eid al-Fitr which IIRC is the end of Ramadan, a sort of muzzie yuletide.
The postal jerk tried to sell me one, I said “No! I want a flag stamp.”
He said “But they both cost the same.”
Clueless.....low information voter.
You are exactly right. I just looked at the letter and the stamp says EID Greetings.