It could also be built using assembler code, would you like to learn that as well?
Seriously though, xml is not a programming framework. It is a method of data representation that is considered useful because so many different systems have decided to use it and the rules of usage are normally clearly defined. This means that it is well suited to interoparability between heterogenous systems.
There is no way xml can create emails. Some of the associated technologies, XSLT for instance, can make xml a good way to store and re-use data in multiple ways but it is certainly not a programming language.
What technology do you use at present on your site, ASP, PHP or something else. Once we know that we could advise on adding emailing features.