Having trouble getting Magento to send transactional emails after making some changes

Basically I had Ebizmart Mandrill extension installed, which I was using its SMTP to send transactional emails. Then I installed ASCHRODER SMTP-PRO , since I wanted to switch over to using SendGrid instead of Mandrill. After installing this new module, I then uninistalled the Ebizmart Mandrill extension, and then reinstalled yet again the Aschroder extension. Now my Magento store doesn't send out any transactional emails (but when I run a "Test" on the [login to view URL] module config page, the test works just fine/successfully).