Domino is working as expected. If there is a forwarding address in a person document, Domino will resolve this when the user hits send.
If the user attempts to resolve the address before sending it then they will see the forwarded address.
It is possible to mask the forwarding address momentarily by adding @DominoDomain on the end of the forwarding address, however this will be replaced as soon as the address is resolved; either by the user pressing F9 or sending the email.
Domino and Notes are working as designed and there is nothing that can be done by MNE to mitigate this issue.
