메일 타입을 HTML로 해서
이미지 데이터를 포함시킨다.
NSData *imageData = UIImageJPEGRepresentation(myImage, 1.0f);
NSString *encodedString = [imageData base64Encoding];
[emailBody appendString:[NSString stringWithFormat:@"<p><b><img src='https://t1.daumcdn.net/cfile/tistory/275C1D4656E67CA00C",encodedString]];
http://stackoverflow.com/questions/14859463/how-to-send-image-in-email-body