Charles Sprickman via Postfix-users:
>
>
> > On Jun 7, 2026, at 10:18?AM, Wietse Venema via Postfix-users
> > <[email protected]> wrote:
> >
> > Charles Sprickman via Postfix-users:
> >> Jun 6 20:37:19 mbox postfix/postscreen[23313]: warning:
> >> psc_dnsbl_request: connect to private/dnsblog service: Connection refused
> >> Jun 6 20:37:19 mbox last message repeated 30 times
> >
> > The dnsblog service in master.cf requires a 'zero' process count
> > limit, and your master.cf is configured accordingly.
> >
> > This means that some other resource limit is in effect. Perhaps a case of
> > https://web.archive.org/web/20230309014619/http://dilbert.com/strip/1995-06-24
>
> Oh no! :)
:-)
> I have many jails running on this thing, but overall, not a very
> demanding load.
Perhaps each jail has reduced resource limits (so that it performs
like Dilbert's under-powered computer).
> So self-imposed resource limits? I can check per-user proc counts,
> memory, sockets, anything specific? Should dnsblog be logging
> anything here or I just have to rely on postscreen telling me it
> can't connect to dnsblog?
<wild-ass speculation>
When a spammer makes a huge burst of connections to your server,
those connections are handled by a postscreen daemon. The large
number of simultaneous connections exhausts some networking resources.
Then, when postscreen requests a connection to a dnsblog process,
that connection request fails with error code ECONNREFUSED.
</wild-ass speculation>
Wietse
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