Arbooks reply worked for me and is spot on!  After not being able to send emails for at least a couple years, I finally can do so again.  I have a yahoo email and never knew I needed to use a separate password for Quickbooks to be able to send emails on my behalf-you cannot use your normal password when Quickbooks prompts you to enter a password!  It has to be a special third-party password generated by Yahoo.  I cannot thank Arbooks enough, such a lifesaver, I hope others find it helpful as well.  Please see their post above, I'm sure I'm not explaining it very well, but they do a great job, and you can also google how to get a third-party password for yahoo email accounts and answers will come up there as well.