Good question - we build our connectors through the APIs of external companies (Smartsheet being one), and after reviewing Smartsheet's API documentation just now, it looks like there is currently no way to expand their sheet or row attachments into a full email attachment. If you use Gmail, we are working on a method to send an email from Gmail with an attachment which, once completed, will allow you to build a custom email including any attachments and/or sheet information that you want to download from Smartsheet.
However, once that's completed, I'm afraid there's no simple way for us to accommodate this use case. I will likely be working on that Gmail method in a couple weeks or so, and I'll let you know here when it's complete!
As always, thanks for using Azuqua, and the Community forum in particular!