Just one other thing I found it hard to get back to the shopping cart when an item was placed in it. The only way I could find to checkout was to put another item in the basket.

I had the same problem with the email and found that to sort it out I had to re-setup the email including the server. ie delete sales at what.com and then reinstall it and that se it up again in Zencart. Are you having problems with the checkout confirmation, if so then this is the way to sort out the problem