How to validate an email id..?

Way 1.

NSString *email = textFieldemail.text;
NSString *emailRegEx =
@"(?:[a-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[a-z0-9!#$%\\&'*+/=?\\^_`{|}"
@"~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\"
@"x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[a-z0-9](?:[a-"
@"z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-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-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];
BOOL myStringMatchesRegEx = [regExPredicate evaluateWithObject:email];


if(!myStringMatchesRegEx)
{
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"email" message:@"Email id is invalid, please provide a valid email id." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release];
}
else
[self prepareHmlDataAndSendEmail];

Way 2.

if (! (([txtMailId.text rangeOfString:@"@"].location != NSNotFound) && ([txtMailId.text rangeOfString:@"."].location != NSNotFound) && [txtMailId.text rangeOfString:@"@"].location < [txtMailId.text rangeOfString:@"."].location ) )
{
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"email" message:@"Email id is invalid, please provide a valid email id." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release];
}
else
[self prepareHmlDataAndSendEmail];

Way 3.

NSArray *validateAtSymbol = [txtLoginId.text componentsSeparatedByString:@"@"];
NSArray *validateDotSymbol = [txtLoginId.text componentsSeparatedByString:@"."];
if(([validateAtSymbol count] != 2) || ([validateDotSymbol count] < 2))
{      
UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:nil message:@"Invalid EMail Address" delegate:self cancelButtonTitle:nil otherButtonTitles:@"Ok", nil];
[alertView show];
[alertView release];
}