First... check the obvious. Have him try to send you an email to that same address and see if that goes through. Be sure the email he is trying to send it to is spelled correctly.., Is he typing it in.., or copy and pasting. (less chance for mis spellings/errors). Second.., is it a Country thing..., maybe his account cannot send to certain countries; or your account cannot receive from certain countries.. Hope that helps...
I agree to what xTimelinex has said. Most often, the paypal email has been misspelled, or you have given the wrong Paypal. Or perhaps, he lives in a country like India wherein they can't send money to fellow Indians. Indian to Indian, it should be through bank account. Indian to other countries and vice versa, it's okay.
Please double check the spellings of ID. It can be the only reason. Because even limited paypal can receive payments.
also be sure that you paypal account is linked with a bank account I thought you could just set one up and use it only online but you have to do the whole bank confirmation thing