Unblocking email on a mac with Msn

Hello,

A friend of mine has the same problem as below, but she uses a MAC and MSN for email.

Hello, both my dad and me are using hotmail. since last september he has not been able to recieve emails from me. they do not even show up in his junk folder. is it possible that he has blocked my email address by mistake ? if this is the case how do we go about unblocking it ? thanks.