regex - how does one validate the "." in e-mail addresses? -

i have following method validate e-mail addresses in form.

 -(bool) validemailaddress:(nsstring*) emailstring {     nsstring *regexpattern = @"^[a-z0-9._%+-]+@[a-z0-9.-]+.[a-z]{2,4}$";     nsregularexpression *regex = [[nsregularexpression alloc] initwithpattern:regexpattern options:nsregularexpressioncaseinsensitive error:nil];     nsuinteger regexmatches = [regex numberofmatchesinstring:emailstring options:0 range:nsmakerange(0, [emailstring length])];     if (regexmatches == 0)          return no; // email invalid      else         return yes; // email valid    } 

this works great except breaks down if user gives e-mail of "abc@xyz" (without super domain .com or .org).

i'm pretty sure problem has "." in regex. tried escaping this,

nsstring *regexpattern = @"^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$"; 

but doesn't work, either. suggestions?

edit: didn't put in escape before last dot when posting question. sorry.

i don't see escape sequence in last example. try:

nsstring *regexpattern = @"^[a-z0-9._%+-]+@[a-z0-9.-]+\\.[a-z]{2,4}$";