I am using version 3.2.3 of Seamless Donations with version 3.9.1 of wordpress. I've been doing testing using my sandbox personal account. However, I've never once received a Thank You email. So my question is, do Thank You emails get sent out when you're testing against the Paypal sandbox?
As a side note, when I click the "Send Test Email" in the wordpress admin console for the Seamless Donations plugin, I receive that email just fine, so I know that my site has no problems actually sending emails.