eMail validation on iphone

- (BOOL) validateEmail:(NSString*)email
{
    if( (0 != [email rangeOfString:@"@"].length) &&  (0 != [email rangeOfString:@"."].length) )
    {
        NSMutableCharacterSet *invalidCharSet = [[[[NSCharacterSet alphanumericCharacterSet] invertedSet]mutableCopy]autorelease];
        [invalidCharSet removeCharactersInString:@"_-"];
       
        NSRange range1 = [email rangeOfString:@"@" options:NSCaseInsensitiveSearch];
       
        // If username part contains any character other than "."  "_" "-"
       
        NSString *usernamePart = [email substringToIndex:range1.location];
        NSArray *stringsArray1 = [usernamePart componentsSeparatedByString:@"."];
        for (NSString *string in stringsArray1) {
            NSRange rangeOfInavlidChars=[string rangeOfCharacterFromSet: invalidCharSet];
            if(rangeOfInavlidChars.length !=0 || [string isEqualToString:@""])
                return NO;
        }
       
        NSString *domainPart = [email substringFromIndex:range1.location+1];
        NSArray *stringsArray2 = [domainPart componentsSeparatedByString:@"."];
       
        for (NSString *string in stringsArray2) {
            NSRange rangeOfInavlidChars=[string rangeOfCharacterFromSet:invalidCharSet];
            if(rangeOfInavlidChars.length !=0 || [string isEqualToString:@""])
                return NO;
        }
       
        return YES;
    }
    else // no '@' or '.' present
        return NO;
}