return mail

A friend of mine has 2 e-mail address’s. The first @sasktel.com;the second @saskel.com. The messages are sent to me from saskel and I must return/reply to sasktel.I’m not sure why he has seperate address’s for sending and recieving.In order for me to return mail I must send new e-mail;as it is I’m unable to reply to each post with these 2 e-mail address;I recieve return mail.Is there anyway that I can eliminate the incorrect address and reply to the correct one.When I reply the address bookshows 2 address’s. The incorrect one “saskel” is addressed in the reply post and I must add the correct address “sasktel” thanks