Problems extracting attachment from email

[foten]

Hi community,

This is the task I'm struggling with:
- A user sends me an email with the subject '*****3gp*****'
  including an attached .3gp-file.
- I then fetch that email, extracts the attachement and stores
  it localy as a file.
- I then run a python-script that parses the stored file
  and generates an excel-file with statistics of that file
  at a shared driver.
  
I'm using getmail (http://pyropus.ca/software/getmail/)
(running on cygwin with cygwin python 2.4)
and the filter function provided to fetch my mail. getmail
starts my filter script and the mail is send using stdin.

I then read from stdin using
        sys.stdin.read()
and the message is stored locally. The content of this stored file
is exactly the same as the mail sent to me.

I then parse that message using
        fp = open(tmp_file,'rb')
        p = email.Parser.Parser()

The problem I'm having is when I'm trying to extract the
attachement using
        f=open(Filename, "wb")
        f.write(msg.get_payload(decode=1))
        f.close()
Not the whole message is decoded and stored!
When only trying
        f.write(msg.get_payload())
I see that the last 255 bytes are missing.

How is this possible, I receive every last byte from stdin?

I then tried calling my windows python installation (2.4) instead of
the cygwin thingie, but that didn't work either.

Doing this using IDLE for windows or a cmdprompt for cygwin works
great!

Any ideas 'bout what I'm doing wrong here?

cheers

//Fredrik