Microsoft Exchange Server handles multiple internet domains fine but when sending out email to the internet only one SMTP smart host is used via the Exchange send connector. It's possible to create more than one send connectors and it even is possible to associate a send connector with a domain name but that only works for the receiving domain. It is not possible to have different SMTP smart hosts based on the sender domain in Exchange. MultiSendcon solves that problem. It distributes email sent out from Exchange to separate SMTP smart hosts with different SMTP AUTH usernames and passwords according to the sender address. That way you can have outgoing emails sent from your normal company email addresses routed through the web space provider's SMTP relay server and have emails sent from an Exchange-hosted googlemail address routed through googles SMTP relays automatically.