Hello,
I ran into the same issue emailing estimates and I assume I couldn't email invoices as well, though I never tried. Here is what I did after exploring the rabbit hole of hotmail settings, ports not open in my firewall, 2 level authentications, etc.
I went into Edit|Preferences and clicked on Send Forms.
On the My Preferences Tab I went down to my email address under Email IDS
I clicked on the email address and clicked the "Edit" button at the bottom of the window
I unchecked "use enhanced security"
I clicked OK.
It then sent me to my MSN Hotmail access page and allowed me to enter my password.
It told me that Quickbooks Desktop was now connected to my Microsoft Email account and it sent me an email verifying that.
Quickbooks then prompted me to go back in and re-check "use enhanced security".
I then went and tested....sure enough it asked for my email password like it always does once each session.
I entered the password and the estimate was sent.
PROBLEM SOLVED....hope that helps others....
