EMail Regex RFC 2822

A little objective-c snippet for finding a valid email. Current implementation, allows uppercase characters which goes against standard. RFC2822 standard is commented out below:

- (BOOL)validateEmail:(NSString *)email {
   //RFC 2822 Email Implementation
   if ([email length] == 0) {
       return NO;
   }
   //Practical Implementation w/ allowing uppercase characters
   NSString *emailRegex = @"[A-Za-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[A-Za-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?\\.)+[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?";

   //Alternative for TRUE RFC2822 compliance w/ uppercase characters
   //@"(?:[A-Za-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[A-Za-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?\\.)+[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?|\\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[A-Za-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])";

   NSPredicate *regExPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
   if ([regExPredicate evaluateWithObject:email])
   {
       return YES;
   }
   else
   {
       return NO;
   }
}

Enjoy!