Not the OP but, I can confirm that iMessage works perfectly in Iran; However, because of both economical situation (inflation and the higher price of iPhone comparing to average Android phones) and the fact that local companies cannot release their apps on the AppStore, only a small portion of people use iPhone or in this case iMessage.

I’m not Iranian, but I spent a lot of time over this for a friend. iMessage works ok once you are able to activate it. But Apple insists on contacting “init-p01md.apple.com” with plaintext HTTP, this sometimes connects successfully, but often it doesn't.