It seems that the address of the sender which comes with the message and
used when replying is incorrect. You would have to get the correct address
and ask the person to correct it in their Account properties, E-mail Address
or Reply Address, else you have to retype the correct address when ever you
want to reply.
Have you ever been able to send a message to that address? If so, might you
have a copy of such message so you can compare the address used then to the
one in the latest messages you receive but cannot answer to?
HTH
I can send emails to most addresses on outlook 2000, but there is a certain
address that I can receive from but cannot send message back
