Out of office email stuck in queue as MSMilter give out a 4.7.1 Service unavailable

J-P Methot jp.methot at planethoster.info
Fri May 5 18:31:42 UTC 2023

I may have found something regarding this.

With debug enabled, I can see in the journalctl logs the following error 
every time the server should send me an autoresponse :

SMFIC_MAIL: bad packet

The message then repeat itself every minute or so until I manually 
discard messages in the queue, then it doesn't reappear. A google search 
for that error message leads me there:


We are indeed working with non-smtp mail in this case, so could it be 
hitting a similar bug? What I think could be happening is that postfix 
tries to flush its queue every minute or so but can't as it hits this 
bug, thus generating a recurring bad packet error in MSmilter.

On 5/4/23 18:16, Shawn Iverson wrote:
> I'm not sure why that is happening and may require setting Debug in 
> MailScanner and restarting msmilter to see what is happening via mail 
> log or journalctl.
> Another option since that is is to set Milter Ignore 
> Loopback = true but I'm not sure you want that behavior since emails 
> will bypass MailScanner coming from the localhost.
> On Thu, May 4, 2023, 6:05 PM J-P Methot via MailScanner 
> <mailscanner at lists.mailscanner.info> wrote:
>     Hi,
>     I'm testing Mailscanner 5.3.3 and Postfix 3.6.2. Postfix and
>     Mailscanner
>     are on two different servers. Everything works properly, except if
>     I set
>     an autoresponse in roundcube, the email gets stuck in the postfix
>     queue
>     with a temporary failure message :
>     milter-reject: MAIL from localhost[]: 4.7.1 Service
>     unavailable
>     - try again later; from=<>
>     Postfix has three milter setup : opendkim, opendmarc and MSMilter,
>     though that last one is written as an IP + port. If I remove MSMilter
>     from the list, the email go through without issue. So what I
>     understand
>     is that the  Mailscanner milter is not even accepting my email to
>     scan
>     it, but instead rejecting it with a temporary failure message, as
>     if the
>     server was greylisted. Yet, nothing inside Mailscanner indicates
>     that,
>     as the email just sits in queue inside postfix on the origin server.
>     What could explain this behavior? I've tried setting Treat Invalid
>     Watermarks With No Sender as Spam = nothing, but that didn't change
>     anything and as far as I'm aware, the email isn't even given a score.
>     -- 
>     Jean-Philippe Méthot
>     Senior Openstack system administrator
>     Administrateur système Openstack sénior
>     PlanetHoster inc.
>     -- 
>     MailScanner mailing list
>     mailscanner at lists.mailscanner.info
>     http://lists.mailscanner.info/mailman/listinfo/mailscanner
Jean-Philippe Méthot
Senior Openstack system administrator
Administrateur système Openstack sénior
PlanetHoster inc.
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