GnuPG between Sendmail servers

[Claus Assmann]

On Wed, Apr 03, 2002, Oliver Schönrock wrote:
> I need to set up "secure routing of mail" between 2 (or more) Sendmail SMTP 
> servers.
> 
> Is it possible to somehow connect gpg into the loop? How do you deal with 

Why do you want to use gpg when there is a standard for SMTP,
that is already implemented in sendmail?

> the fact that many messages will have to share the same key pair which is 
> known only only by the 2 servers. The receiving server will have to decrypt 
> and then perform its normal routing functions. The clients where the 
> messages originate and are received should know nothing of the encryption.
> 
> Is this doable?
> 
> Will I have to write code or can sendmail/gpg be configured to make this 
> possible?
> 
> Does anyone have any experience with this?

STARTTLS is implemented by sendmail (since version 8.11).  You don't
need to write any extra software for this.  You can enforce that
all mails between those two hosts are encrypted (and authenticated).

See: http://www.sendmail.org/~ca/email/starttls.html