Can't attach CSV file with Mail for iPhone

The code below works perfectly to send text (.txt) attachments via the mail application (textfile.csv needs to be modified everywhere with textfile.txt). However when I try to attach csv files it does not work at all (the mail application opens up showing the icon of the textfile.csv but when the mail arrives it has no attachment - nor the data is displayed within the message body). No difference if I change the mime type to "text/plain". I am puzzled... What am I doing wrong?? Any ideas please?

Code:

- (NSString *)getPath {
   NSString *paths = [NSSearchPathForDirectoriesInDomains
   (NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
   return [paths stringByAppendingPathComponent:@"textfile.csv"];
}

//Saves file to Documents folder
//Method writes a string to a text file
-(void) writeToTextFile{
 //get the documents directory:
 NSArray *paths = NSSearchPathForDirectoriesInDomains
 (NSDocumentDirectory, NSUserDomainMask, YES);
 NSString *documentsDirectory = [paths objectAtIndex:0];


 //make a file name to write the data to using the documents  directory:
 NSString *fileName = [NSString stringWithFormat:@"textfile.csv", 
 documentsDirectory];
 //create content
 NSString *content = @"One,Two,Three,Four,Five";

 //save content to the documents directory
 [content writeToFile:fileName 
     atomically:NO 
    encoding:NSStringEncodingConversionAllowLossy 


 error:nil]; 
}

// Displays an email composition interface inside the application. Populates all the Mail fields.
-(void)displayComposerSheet
{ 
MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
 picker.mailComposeDelegate = self; 
 [picker setSubject:@"Subject"];

 // Set up recipients
 NSArray *toRecipients = [NSArray arrayWithObject:@"email@domain.com"];

 [picker setToRecipients:toRecipients];
 // Fill out the email body text
 NSString *emailBody = (@"Data is attached as a .CSV file");

 [picker setMessageBody:emailBody isHTML:NO];

 NSString *SavedDataPath = [self getPath];
 NSString *path = SavedDataPath;

 NSData *myData = [NSData dataWithContentsOfFile:path];
    [picker addAttachmentData:myData mimeType:@"text/csv" fileName:@"textfile.csv"];  

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