NSString category to test if a string is a valid e-mail address.

NSString+EmailValidating.h

//
//  NSString+EmailValidating.h
//  
//
//  Created by Rems on 11/12/12.
//  Copyright (c) 2012 . All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (EmailValidating)

#pragma mark - Valid email
//! Valid if a NSString ivar is a valid email address.
//! @param [in] string : The NSString to check if it is a valid email address.
- (BOOL)isValidEmail;

@end

NSString+EmailValidating.m

//
//  NSString+EmailValidating.m
//  
//
//  Created by Rems on 11/12/12.
//  Copyright (c) 2012 . All rights reserved.
//

#import "NSString+EmailValidating.h"

@implementation NSString (EmailValidating)


#pragma mark - Valid email

/**
 @brief Valid if a NSString ivar is a valid email address.
 @author : Rémi Lavedrine
 @date : 11/12/2012
 @remarks : <#(optional)#>
 */
- (BOOL)isValidEmail
{
    BOOL stricterFilter = YES; // Discussion http://blog.logichigh.com/2010/09/02/validating-an-e-mail-address/
    NSString *stricterFilterString = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
    NSString *laxString = @".+@.+\\.[A-Za-z]{2}[A-Za-z]*";
    NSString *emailRegex = stricterFilter ? stricterFilterString : laxString;
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
    return [emailTest evaluateWithObject:self];
}

@end