I have access to (and send as permissions to) an account called Support.
If I send any email (either a reply to an existing one or a new message) that is sent FROM Support and I track it in CRM, the message is tracked in CRM but is saved to my drafts folder in Outlook. The recipient does not receive the message.
I can "send as" if I don't track the e-mail. I can also send from my account, both with and without tracking. In these cases the recipient does receive the e-mail.
I thereofre suspect it is down to tracking e-mails that are sent with Send As permissions.
Client machine is Windows XP Pro SP3 with Office Outlook 2007 SP1 & CRM 4.0 Client with Rollup 4.
CRM is partner hosted, but we are using our own email server.