function IsEMail(EMail: String): Boolean;
var s: String;ETpos: Integer;
begin
ETpos:= pos('@', EMail);
if ETpos > 1 then
begin
s:= copy(EMail,ETpos+1,Length(EMail));
if (pos('.', s) > 1) and (pos('.', s) < length(s)) then
Result:= true else Result:= false;
end
else
Result:= false;
end;

（出处：http://www2.delphifans.com/blog/more.asp?name=caixiaoming&id=389）