Why are .CAB attachments I fetch with imaplib corrupt?

Question

I have an email that I am trying to download the attachment from, using imaplib.

I am using the Email library to translate messages to the email.message class. This is working perfectly for all of the emails I am dealing with, but when I fetch this attachment, the file looks intact, and using Notepad++'s compare, matches the original cab file downloaded through Thunderbird.

This is an example of the code I am using.

fileContents = message.get_payload()[1].get_payload(decode=True)  #
fileName = message.get_payload()[1].get_filename()
with open(fileName, 'w') as f:
    f.write(fileContents)

As I said, the file contents appear identical to the original file downloaded through other clients. It has the same size, precisely. However, when I open the downloaded file in WinRar, 7zip or using Window's EXPAND.exe, it gives the following message.

!   H:\Code\Backup Monitor\backupsite\tst.CAB: The archive is corrupt

Does anyone have any idea why this might be happening?

Answer 1

I fixed my own issue. I needed to be opening the file in binary mode as well.

So

with open(fileName, 'w') as f:

becomes

with open(fileName, 'wb') as f: