SMTP messages that are sent from the Lotus Notes SMTPMTA to Exchange 2000 and to Exchange 2003 append @NotesDomain to the sender's address

SMTP messages that are sent from the Lotus Notes SMTPMTA to Exchange 2000 and to Exchange 2003 append @NotesDomain to the sender's address.
To do this, modify the following mapping tables:
Edit the following SMTP address in the Amap.tbl mapping tables. You can find these tables under the Exchsrvr\conndata\dxamex folder path:
InetAddr 128 proxyAddresses(SMTP:)
Edit the following SMTP address in the Amap.tbl mapping tables. You can find these tables under the Exchsrvr\conndata\dxanotes folder path:
InetAddr 128 InternetAddressNotes
For the line in the Amap.tbl file of the Dxamex folder, if the word SMTP is uppercase, the primary bold SMTP address syncs from Exchange to Notes. If the word smtp is lowercase, one of the secondary smtp addresses will be synced. Both of these entries are required for the sync to work.
If you only want to sync in one direction, such as to sync an Exchange server to a Lotus Notes server when the Lotus Notes server is the SMTP gateway, you have to change the SMTP address in the Amap.tbl file of the Dxanotes folder to the following entry:
InetAddr 128 InternetAddress 1 The "1" at the end of the SMTP address sets the value to read-only. Therefore, the Dirsync process will not write the SMTP address of the Notes user to the contact in Active Directory.
After you have made the changes, restart the Microsoft Exchange Connectivity Controller service and the Microsoft Exchange Connector for Lotus Notes service. Then force a full reload of the Dirsync process. You can force the reload in both of directions, or you can force the reload only from Exchange to Lotus Notes if you want to sync only one direction and Lotus Notes is the SMTP gateway to Exchange.Note After you upgrade to the latest Exchange Server 2003 post-Service Pack 2 Web Release, "@NotesDomain" will still be appended to the sender's display name of incoming e-mail from external Internet domains. However, this behavior will no longer affect message flow.

Ref: http://support.microsoft.com/kb/255160