First you would have to go to one of your nds games that supports wifi and connect to your network. Then you would have to download something like DS Organize or NDS Mail to access your email. This isn't really easy for beginners.
Well, actually, you can use the wifi-connection of your NDS with DSOrganize
You don't need anything else than your NDS with adapter (TTDS or any other) and µSDCard AND an active Wifi hotspot. It even has a configuration setting for Wifi. But, as already said here before, don't expect to much of it! It does work, but it is very slow ...
My EZ Flash 3in1 plus RAM portion is super fast. Opera DS is fast in my side. I always think that the RAM is somewhat similar with that of a DSi. It's 16MB after all for the 3in1plus and the DSi. I dont complain on my DS Lite Browser