iPhone API已经提供了系统写邮件界面的接口,使用MFMailComposeViewController，用来显示界面.   
项目中需要添加MessageUi.framework。头文件加入MFMailComposeViewControllerDelegate。#import <MessageUI/MessageUI.h>   
sendMailViewController.m文件的实现：   
- (void)viewDidLoad   
{   
    UIButton *button = [UIButton buttonWithType: UIButtonTypeRoundedRect];   
    button.frame = CGRectMake(0, 40, 320, 50);   
    [button setTitle: @"Mail" forState: UIControlStateNormal];   
    [button addTarget: self action: @selector(sendEMail) forControlEvents: UIControlEventTouchUpInside];   
    [self.view addSubview: button];   
}   
 
- (void) alertWithTitle: (NSString *)_title_ msg: (NSString *)msg    
{   
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:_title_    
                                                    message:msg    
                                                   delegate:nil    
                                          cancelButtonTitle:@"确定"    
                                          otherButtonTitles:nil];   
    [alert show];   
    [alert release];   
}    
 
//点击按钮后，触发这个方法   
-(void)sendEMail    
{   
    Class mailClass = (NSClassFromString(@"MFMailComposeViewController"));   
 
    if (mailClass != nil)   
    {   
        if ([mailClass canSendMail])   
        {   
            [self displayComposerSheet];   
        }    
        else    
        {   
            [self launchMailAppOnDevice];   
        }   
    }    
    else    
    {   
        [self launchMailAppOnDevice];   
    }       
}   
//可以发送邮件的话   
-(void)displayComposerSheet    
{   
    MFMailComposeViewController *mailPicker = [[MFMailComposeViewController alloc] init];   
 
    mailPicker.mailComposeDelegate = self;   
 
    //设置主题   
    [mailPicker setSubject: @"eMail主题"];   
 
    // 添加发送者   
    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", nil];   
    [mailPicker setToRecipients: toRecipients];   
    //[picker setCcRecipients:ccRecipients];       
    //[picker setBccRecipients:bccRecipients];   
 
    // 添加图片   
    UIImage *addPic = [UIImage imageNamed: @"123.jpg"];   
    NSData *imageData = UIImagePNGRepresentation(addPic);            // png   
    // NSData *imageData = UIImageJPEGRepresentation(addPic, 1);    // jpeg   
    [mailPicker addAttachmentData: imageData mimeType: @"" fileName: @"123.jpg"];   
 
    NSString *emailBody = @"eMail 正文";   
    [mailPicker setMessageBody:emailBody isHTML:YES];   
 
    [self presentModalViewController: mailPicker animated:YES];   
    [mailPicker release];   
}   
-(void)launchMailAppOnDevice   
{   
    NSString *recipients = @"mailto:first@example.com&subject=my email!";   
    //@"mailto:first@example.com?cc=second@example.com,third@example.com&subject=my email!";   
    NSString *body = @"&body=email body!";   
 
    NSString *email = [NSString stringWithFormat:@"%@%@", recipients, body];   
    email = [email stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];   
 
    [[UIApplication sharedApplication] openURL: [NSURL URLWithString:email]];   
}   
- (void)mailComposeController:(MFMailComposeViewController *)controller    
          didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error    
{   
    NSString *msg;   
 
    switch (result)    
    {   
        case MFMailComposeResultCancelled:   
            msg = @"邮件发送取消";   
            break;   
        case MFMailComposeResultSaved:   
            msg = @"邮件保存成功";   
            [self alertWithTitle:nil msg:msg];   
            break;   
        case MFMailComposeResultSent:   
            msg = @"邮件发送成功";   
            [self alertWithTitle:nil msg:msg];   
            break;   
        case MFMailComposeResultFailed:   
            msg = @"邮件发送失败";   
            [self alertWithTitle:nil msg:msg];   
            break;   
        default:   
            break;   
    }   
 
    [self dismissModalViewControllerAnimated:YES];   
}