I don't know. When I use the Send-to-Email toolbar menu to email books to my Kindle, it works fine, gets delivered properly, and a copy of the email shows up in my Gmail "Sent Mail" folder.
Perhaps your email address is not properly configured in calibre? What are your current settings?
For perspective, my settings* are as follows:
Code:
# relay host
relay_host = u'smtp.gmail.com'
# relay port
relay_port = 587
# relay username
relay_username = u'************@gmail.com'
# relay password
relay_password = '*****************'
# encryption
encryption = 'TLS'
...
I am not really sure what you mean by "highlighted the book in Calibre and followed the path to the file". Do you mean, you used a Windows Explorer menu to send the ebook file via Outlook?
* -- copy-pasted from smtp.py in my calibre configuration directory, since I was too lazy to open calibre just to copy-paste my email settings. Also, easier copy-paste.