Attaching a txt-file in mailcomposer ios 7 - ios

Question

When use my following script, then the picture and the logfile would be a attached file. Also some other Text (the default signature) from the email would be attached as index.htm to the email when i open it with Outlook.
The Email is sent out from the iPad with iOS 7.0.6
In the Mail-Application on the Mac, the Files are in the middle of the text, before the signature of the mail-application would be written.
When i attach only the image, then all would be fine. When i attache also the logfile.txt, then its like I have descripted and in the Mail-Application of the mac, all special keys (german like ä, ü) are not decoded as utf8.
Where did I make the mistake?
MFMailComposeViewController *controller = [[MFMailComposeViewController alloc] init];
controller.mailComposeDelegate = self;
currentIOS = [[UIDevice currentDevice] systemVersion];
vNumber = #"V"VersionNumber;
subject = [NSString stringWithFormat:#"%# - Meine aktuelle iPad-Nummer",vNumber];
message = [NSString stringWithFormat:#"<p>Hallo liebes EDV-Team,</p> <p>mein Betriebssystem ist: %#</p><p>Und meine iPad-Nummer lautet: %#</p>", currentIOS, udid];
[controller setToRecipients: [NSArray arrayWithObjects:#"email#webpage.de", nil]];
[controller setSubject:subject];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *txtFilePath = [documentsDirectory stringByAppendingPathComponent:#"logfile.txt"];
NSData *noteData = [NSData dataWithContentsOfFile:txtFilePath];
[controller addAttachmentData:noteData mimeType:#"text/plain" fileName:#"logfile.txt"];
UIImage *roboPic = [UIImage imageNamed:#"world_smilie.png"];
NSData *imageData = UIImagePNGRepresentation(roboPic);
[controller addAttachmentData:imageData mimeType:#"image/png" fileName:#"smile.png"];
[controller setMessageBody:message isHTML:YES];
if ([self respondsToSelector:#selector(presentViewController:animated:completion:)]){
[self presentViewController:controller animated:YES completion:nil];
}
I changed the code for the textfile:
I change the code like elio.d told me:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *txtFilePath = [documentsDirectory stringByAppendingPathComponent:#"logfile.txt"];
NSString *txtFileContent = [NSString stringWithContentsOfFile:txtFilePath encoding:NSUTF8StringEncoding error:nil];
NSData *txtFileData = [txtFileContent dataUsingEncoding:NSUTF8StringEncoding];
[controller addAttachmentData:txtFileData
mimeType:#"text/plain"
fileName:#"logfile.txt"];
The logfile.txt would be attached but the signature from the ipad would be attached to the email in ATT00002.htm and now i got also a empty ATT00001.htm
I have the same problem when i change the type of the email (isHTML:NO)