static server boolean validateEmail(EMail _eMail)
{
Str MatchEmailPattern = @”^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$”;
System.Text.RegularExpressions.Match myMatch;
boolean ret;
;
// InteropPermission to execute COM/DLL object server side
// Design priciple to have inside outermost exception handling structure try-catch-ttsscope to control state
// new InteropPermission(InteropKind::ComInterop).assert();
new InteropPermission(InteropKind::ClrInterop).assert();

try
{
myMatch = System.Text.RegularExpressions.Regex::Match(_eMail, MatchEmailPattern);
ret = myMatch.get_Success();

}
catch (Exception::Error)
{

}

// Design priciple to have inside outermost exception handling structure try-catch-ttsscope to control state
CodeAccessPermission::revertAssert();

return ret;
}

public static void main(Args args)
{;
Info(strFmt(”%1″, class1::validateEmail(”nn@dr.dk”)));
Info(strFmt(”%1″, class1::validateEmail(”nn@@dr.dk”)));
}

I guess you mean the first method there.
I just tried it myself one more time to be sure, and it worked fine.
rikky@haxx.net returned true
rikky@haxx.nettt returned false

This was in AX 2009.
Make sure you have .NET framework installed!