Edge Server blocking some zip attachments

[malaka]

The Edge server is occassionally blocking zip file attachments with an error message of: 550 5.7.1 Message rejected due to unacceptable attachments

If I unzip the attachment and extract the files then rezip, the Edge server allows it through.

This affected a user back in October, but we couldn't find anything so thought it might have been a one time hiccup, but just had it happen to another user today.

Any ideas?

 

[xmsre]

What client did they use/how was the attachment encoded?

When you attach a document, it gets encoded as a specific MIME type that should match the file extention. Lots of times different clients or applications don't encode an attachment with the correct MIME type, and use application/octet-stream instead. Application/octet-stream is often blocked for security reasons.

 

[Zelandakh]

Anything in the event log to help us?

 

[malaka]

He's using Outlook 2003 and WinZip 8.1. If I try to send his version of the zip file it bounces. My rezipped version (also done with 8.1) does make it through. I am sending from Outlook 2007 instead of 2003, I wonder if that could affect anything.

Nothing in the Event Log on the Edge, mail server, or my machine.

 

[xmsre]

If you can get your hads on the failed email, check the MIME headers for the attachment part and see how was encoded.

 

[malaka]

This is in the bounce message:

Content-Type: multipart/mixed;
boundary="_004_76BEEAE3D5177B419EFD76DBC1BAE8930267B4417CD2ssmx03aquil_"
MIME-Version: 1.0

Does that look correct or is there something else I should be looking for?

 

[xmsre]

Need to see the headers for the attachment part. Something like:

------=_NextPart_000_0158_01C91E22.7B6CF7B0
Content-Type: application/pdf;
name="taughtli.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="taughtli.pdf"

is encoded properly and will work. On the other hand, something like:

------=_NextPart_000_0158_01C91E22.7B6CF7B0
Content-Type: application/octet-stream;
name="squarekn.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="squarekn.pdf"

is not encoded properly and will be blocked.