Re: Encrypting E-mails

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From: Vanguard (vanguard_stealth_at_yahooNIXTHIS.com)
Date: 01/28/05 

Date: Fri, 28 Jan 2005 17:20:13 -0600

"Scotty" <Scotty@discussions.microsoft.com> wrote in message
news:AC858C98-7035-4E26-B498-ABAFF514B01A@microsoft.com...
> Thanks for the help. I have practiced with sending Digitally Signed
> e-mails,
> but everytime the recipient receives the e-mail it says that the
> e-mail has
> been altered. I am thinking that this might be due to our SMTP server
> adding
> a confidentiality tag to our e-mails. Is there a way around this?

Anti-spam software can sometimes does this on incoming e-mails. Anyone
using a freebie e-mail service that appends promotional spam signatures
onto their outbound e-mails which also end up altering the body of the
message. I don't recall if headers are included in the hash value
calculated for an e-mail but changing anything in the body of the
message will definitely screw up the validity of the encryption. The
recipient can probably still read the message (if the alteration was
before or after the MIME part used to encapsulate the encrypted message)
but they will probably get warned that the digital signature is not
valid.

Rather than add your tag to the body of the e-mail, have you tried
adding it as a header, like "X-<yourcompany>-<tagpurpose>: <string>"?
I've never played around with changing the headers after encrypting a
message. The encryption is a MIME part within the body of the message
so I would suspect you could change the headers with impunity. After
all, every mail server the message bounces through will add to the
headers.

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