Postfix stops accepting connections when primary dns is down.

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Postfix stops accepting connections when primary dns is down.

listserv.traffic
Postfix stops accepting connections when primary dns is down. I'm kind of baffled.
It's probably some really stupid issue that I'm going to hang my head in shame over, but I really can't wrap my head around it.

I've got a postfix box. It's accepting external mail fine. [And has been for some time.]
It's pointed at a couple of caching name-servers in the local network.
Lets call them NS1 NS2.
NS1 is primary and NS2 is secondary.

Recently I noticed that when NS1 is down, postfix won't accept mail.
Yet digs from postfix get handled by NS2 fine, while NS1 is down.
[Just a plain dig, which uses NS2, when NS1 is down. Like so; dig some.f.q.d.n - and the results come from NS2, not NS1.]

Yet, if I change things so NS2 is primary and NS1 is secondary and take down NS1, mail doesn't get interrupted. [And does if I take down NS2]

Can someone give me some places to look that might yield some results?

TIA
-Greg



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Re: Postfix stops accepting connections when primary dns is down.

Viktor Dukhovni
On Fri, Sep 18, 2020 at 07:33:24PM -0700, [hidden email] wrote:

> I've got a postfix box. It's accepting external mail fine. [And has been for some time.]
> It's pointed at a couple of caching name-servers in the local network.
> Lets call them NS1 NS2.
> NS1 is primary and NS2 is secondary.
>
> Recently I noticed that when NS1 is down, postfix won't accept mail.

Disable default domain suffixes in /etc/resolv.conf (and any copy in
/var/spool/postfix/etc if smtpd(8) is chrooted in master).

    /etc/resolv.conf:
        domain .
        search .
        ...

> Yet digs from postfix get handled by NS2 fine, while NS1 is down.

Your forward and/or reverse zones may not be mirrored on the secondary,
or may be expiring too quickly.

--
    Viktor.