Why is my email bouncing when it shouldn't be?

I am trying to send an important email to someone in india, and I live in the US. I sent the email from both my yahoo account and my aol account. This person has email accounts on yahoo and on rediff.com, yet when I try both these accounts, I get mailer daemon notices that say user unknown and service unavailable. However, I'm a hundred percent sure that the yahoo address is correct and that the last time I visited this person was very recently and I know his email account was working then. I'm wondering whether this problem could be because of the bad internet connection he has over in India...there are frequent power shortages and the internet goes down a lot. Could this be the reason for my failed email attempts? I'm really anxious about this, and I really need to send this email as quickly as possible, so I'd greatly appreciate any helpful advice. Thank you!!