Milter-greylist

I've encountered this problem... but with only one domain. Recently I  
set up milter on a moderately busy server, and customers are  
complaining  about the following:

On certain clients:
	k-mail (linux)
	Outlook 5.0.1 (Mac OS9)
	Thunderbird 1.0.7
	pine

Sender immediately receives an error in the form pop-up from their  
SMTP server,
which says: (this differs from client to client)

"An error occurred while sending mail. The mail server responded:  
4.7.1 Greylisting in action, please come back in 00:08:00. Please  
verify that your email address is correct in your Mail preference and  
try again"

or a bounce message as shown below:
> Subject: Mail delivery failed: returning message to sender
> Date: Thursday 01 December 2005 04:21 pm
> From: Mail Delivery System <Mailer- 
> Daemon@...>
> To: eric@...
>
> This message was created automatically by mail delivery software.
>
> A message that you sent could not be delivered to one or more of its
> recipients. This is a permanent error. The following address(es)  
> failed:
>
>   ed@...
>     SMTP error from remote mailer after RCPT TO:<ed@...>:
>     host mail.siriuslink.com [128.121.50.164]: 451 4.7.1  
> Greylisting in
>  action, please come back in 00:26:23: retry timeout exceeded
>
> ------ This is a copy of the message, including all the headers.  
> ------
>
> Return-path: <eric@...>
> Received: from [68.164.67.243] (helo=[192.168.1.102])
> 	by smtpauth01.mail.atl.earthlink.net with asmtp (TLSv1:RC4-MD5:128)
> 	(Exim 4.34)
> 	id 1Ehyg2-0003Ax-P7; Thu, 01 Dec 2005 19:21:27 -0500
> From: Eric Carter <eric@...>
> To: Ed Kelly <ed@...>,
>  Ed Kelly <ed@...>
> Subject: Re: don't forget your...
> User-Agent: KMail/1.8
> References: <3C12D294-F67A-4986-8DA7-47F7816C0C3A@...>
> In-Reply-To: <3C12D294-F67A-4986-8DA7-47F7816C0C3A@...>
> MIME-Version: 1.0
> Date: Thu, 1 Dec 2005 16:21:25 -0800
> Content-Type: Multipart/Mixed;
>   boundary="Boundary-00=_FO5jD5Jq4/UzXk+"
> Message-Id: <200512011621.25179.eric@...>
>