MS CRM 4.0 by default does not allow users to send email to contacts and accounts that do not have an email address. This does seems like a big limitation, espically if you want to foraward an email in MS CRM to an email address that is not assocaited with any account or contact in MS CRM.

The Image below shows the message you get with the default configuration settings.




If you want to be able to send emails to un-resolved email address you can do this by setting the “Allow messages with unresolved e-mail recipients to be sent” option to Yes in the system settings in Administration tab.

The image below shows how you can change the option.