Hi Andrew,

DNN changed the way SMTP passwords are stored in 7.2.2 so SmithCart 4.57 is most likely not compatible with DNN 7.4. I recommend upgrading to the latest version of the Cart. That way you'll be able to take advantage of all the enhancements we have made since 4.57. Check out the Cart's Change Log at the following link: http://www.smith-consulting.com/Products/DotNetNuke-Modules/Shopping-Cart-Module/Change-Log

Let me know if you have any questions.

Thanks!