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Encrypted Attachments in Windows Live Mail Are Not Visible

I'm running Windows Live Mail on both XP and Vista 32-bit systems. I have configured both versions of Live Mail to use digital certificates to enable signing and encrypting emails and attachments. I'm using the latest updates to all software.

I can send signed, encrypted, and signed and encrypted emails and receive all of them without a problem on the systems. However, when I include an attachment (a PDF file), the message body comes through OK but the attachment does not show up. I have no problem with encrypted attachments in Outlook 2003 and 2007. My Live Mail is configured as follows for the Safety Options:

General Tab: Junk E-Mail protection = Low, no other boxes checked
Security Tab:
    Select the Internet Explorer security zone to use = Internet Zone
    Do not allow attachments to be ssaved or opened that could potentially be a virus = Not checked
    Download Images: Block images = not checked
The appropriate Digital IDs are present and set for email use.
I've even added the sender to my Safe Senders list.

What can I do to get attachments to show when the whole email is encrypted?

Thanks for your help
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bwhoncho
Asked:
bwhoncho
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1 Solution
 
ParanormasticCryptographic EngineerCommented:
Are you signing and encrypting the email?  If so, try it without the signature, only the encryption.  Also have the email itself be in plain text instead of rich format.

If you are just trying to encrypt the attachment, you might want to use a zipping program for the attachment that supports certificates.  Remember - you email is only encrypted until they save the attachment to their hard drive, then it isn't encrypted anymore unless they encrypt it again afterwards.  The ZIP file method is good because the attachment can be saved directly and not loose its encryption.
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bwhonchoAuthor Commented:
Paranormastic:

Thanks for replying. I've tried sending attachments when the email was encrypted only and that didn't let me received them in Windows Live Mail. I've also sent signed and encrypted email with an attachment and that didn't work. The attachment I'm testing with is a PDF file, so it should be on the safe file list.

I tried your .zip idea, that didn't work. By the way, Once I save an encrypted attachment outside of the email program it's stored in the clear. If it weren't stored in the clear then WinZip couldn't unzip it and it was able to do that in my test of your suggestion. So encryption is lost when you save an attachment in the file system.
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ParanormasticCryptographic EngineerCommented:
Your zipping program supports adding password based encryption to the file.  Just make sure you aren't using winzip version 9 there was a bug in that.  The recipient could then save the attachment as normal and would still be encrypted that way.

I'm wondering if there might be a size limitation being reached?  When you encrypt something it takes a lot of extra space to do that - are you able to determine what the file size is after encrypting the email + attachment?  PDF files tend to be a bit on the larger end in the first place - after encryption it could be quite large.  You could try a small test.txt file from notepad thats 1 or 2k.
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bwhonchoAuthor Commented:
You're right if my zipping program can encrypt the file then the encrypted zip file would be encrypted again by the mail system and decrypted at the receiving end still leaving the zip encryption. However, there is not a need for this double encryption or keeping the file encrypted at the receiving end.

As for file size, I tested with a 44KB PDF file. The mail transport system can send 1MB+ files (I've tested this because some of the files I need to send are large). Sending small files is no no use to me. Since the mail system can handle large unencrypted files, it should be able to handle large encrypted files. I can see that the sending of large encrypted files works because I read the same email account with Outlook and can receive 1M+ encrypted PDF files that were sent by Windows Live Mail. So the problem is in the handling of the encrypted attachment in the reception of the email by Windows Live Mail.

I expect that there is a configuration parameter or a registry value that needs to be set a particular way to fix this problem, if there is a fix. It's always possible that there is a bug preventing encrypted attachments from showing. There is no reason that the receipt of encrypted attachments shouldn't be handled like they are in Outlook or Thunderbird (which may be my only rational free alternative).,
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ParanormasticCryptographic EngineerCommented:
Yes - I offered that as an alternate method for moving encrypted attachments.  I would not suggest to encrypt the message containing an encrypted attachment.

44kb in a known 1+ MB filter is adequate for testing that concept - I was worried that a 9 MB PDF made it through a 10MB filter, but after encrypting passed that threshold.

For your mailserver, is this an http: address or is it a pop3 address?  Who is the email server provider?
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bwhonchoAuthor Commented:
I found the solution!
In Windows Live Mail go to the Tools | Safety Options menu and choose the Security tab. In the Virus Protection block select the Internet Zone and uncheck the "Do not allow attachments to be saved or opened that could possibly be a virus" option. Then click OK. This setting will let encrypted attachments show up.

There is a second problem that may be causing encrypted attachments to disappear. This can be on either the sending computer or the receiving one. Anti-spam/Anti-virus software may be blocking  the attachments from being sent or received. Test this by turning off such software on both sides and then sending the encrypted email with an attachment. If you received the encrypted attachment, turn back on the anti-virus/anti-spam software on one machine and test again. If that works the the problem is on the other system. If it doesn't work, verify the problem is on just the sending end by turning the anit-virus/anti-spam software on the receiving end (make sure it's off on the sender) and send another message. If that gets through, then the problem is with the sender. If it still doesn't get there, then the problem is at both ends. In either case, you'll have to figure out how to configure your anti- software to work.
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