[CentOS] Unknown mail transport error

[mouss]

Anne Wilson wrote:
> I've just signed a bunch of keys using the caff tools.  A few minutes ago they 
> started bouncing back at me, with the above error.
> 
> Received: by anne-wireless.lydgate.net (Postfix, from userid 500)
>         id CA4B230EF7; Wed, 20 Aug 2008 11:15:39 +0100 (BST)
> MIME-Version: 1.0
> Subject: Your signed PGP key 0x2C4F325BFF906D62
> User-Agent: caff 0.0.0.309 - http://pgp-tools.alioth.debian.org/
> X-Mailer: MIME-tools 5.425 (Entity 5.425)
> Sender: anne <anne at anne-wireless.lydgate.net>
> Content-Type: multipart/encrypted;
>  protocol="application/pgp-encrypted";
>  boundary="----------=_1219227339-4052-1"
> 
> I used the same tools last year without problems, but obviously something is 
> different this year.  Can anyone suggest what's wrong, and what I can do 
> about it?
> 

the answer is probably in postfix logs.