Hi all, I get it done myself... actually in my send mail code i have predefined the mailto id as well as cc and bcc.. and was changing it at the run time that was giving me the NSInvalidArgumentException. Now as i have changed and left it blank to enter the mail to id at runtime it is working perfectly.

Previous Code:

-(void)displayComposerSheet 
{
    MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
    picker.mailComposeDelegate = self;

    [picker setSubject:@"Hello from California!"];


    // Set up recipients
    NSArray *toRecipients = [NSArray arrayWithObject:@"first@example.com"]; 
    NSArray *ccRecipients = [NSArray arrayWithObjects:@"second@example.com", @"third@example.com", nil]; 
    NSArray *bccRecipients = [NSArray arrayWithObject:@"fourth@example.com"]; 

    [picker setToRecipients:toRecipients];
    [picker setCcRecipients:ccRecipients];  
    [picker setBccRecipients:bccRecipients];

    // Attach an image to the email
    NSString *path = [[NSBundle mainBundle] pathForResource:@"rainy" ofType:@"png"];
    NSData *myData = [NSData dataWithContentsOfFile:path];
    [picker addAttachmentData:myData mimeType:@"image/png" fileName:@"rainy"];

    // Fill out the email body text
    NSString *emailBody = @"It is raining in sunny California!";
    [picker setMessageBody:emailBody isHTML:NO];

    [self presentModalViewController:picker animated:YES];
    [picker release];
}

Now, Set up recipients is left blank in the new code. that works fine. Thanks!