Email syntax validation -iPhone Programming

Understanding that iPhone SDK dont support NSPredicate which is there for MAC Apps SDK i wrote an Utility Method to do a syntax validation of email.

-(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;