Why can't I email to my grandson in Iraq on my Yahoo email when I could on my other email service?

The email address did not change and I have verified it is correct however it will not go on my Yahoo email.

Why can't I email to my grandson in Iraq on my Yahoo email when I could on my other email service?
The server may be down by them. I sue yahoo and emailed by brother there all the time. He has come home now, but always had down time. God Bless your Grandson !
Reply:Maybe it don't have clearance.