If your posts are blank except for attachments it is likely that you have your "Preferred Text Type" setting set to "plain" and you are using one of the following email clients:
Apple Mail on iPhone/iPad
SquirrelMail
When you send an email your client has the option of sending plain (unstyled) email, HTML (styled) email or both. In the case of the above email clients they only send HTML email in some cases and if Postie is set to look for plain it won't find any content. The fix is to turn on the "Text Fallback" option.