You are migrating users from Notes to Exchange. At the point of migration you want their new mail to be delivered to their new mail box.
Notes Migrator for Exchange [NME] does not do any Mail routing per se but facilitates in automating the configuration of mail routing in either the Notes [Domino] or Exchange
There are two kinds of mail routing; single name space and subdomains.
Smarthosts or Send Connectors are used depending on where the mail is initially delivered.
If email arrives at the Domino side
Where you maintain the same “company.com” addressing for both the Notes and Exchange Systems.
Mail routing is achieved via Smarthosts
NME will set the Mail System to “other internet mail” and set the forwarding address to the same “company.com” namespace. This means that the person document points to an Internet Mail System and that Notes is no longer responsible for the delivery of messages for that user. All incoming messages for that address will be sent to the Smarthosts. The Smarthosts need to be configured separately and NME will NOT do this for you.
[Sub domains are where you have notes.company.com and exchange.company com as separate namespaces that are used just for avoiding a mail loop.]
DNS is used for mail routing and there are no smarthosts.
If email arrives at the Exchange side
Send Connectors are used to route mail back and forth from Exchange to Notes
NME will set the targetaddress attribute in AD for objects. This means that when a message comes in for an external contact or a mail enabled or mailbox enabled user that has this attribute populated, Exchange will automatically send the message to the configured Send Connector for processing. Exchange assumes it is not responsible for the delivery of the message.
DNS is used for mail routing and there is no need for Send Connectors.