Lafiel Elentari via Postfix-users:
> Hello.
>
> However, sometimes there is a delay of up to 2 seconds.
You can use tcpdump, wireshark, etc. to see the exact timing and
content of network requests and responses.
- How many connections are happening at the same time? There
will be a delay when all Postfix SMTP server processes are busy.
- When does the TCP connection to Postfix complete?
- When is the DNS PTR query sent with the reversed client IP address?
- When does the DNS PTR reply arrive?
- When is the DNS A query sent with the clients name ?
- When does the DNS A reply arrive?
- When does Postfix send the 220 greeting?
- and so on.
Or you can disable the Linux name service crap and then point
/etc/resolv.conf to a public DNS server at 1.1.1.1 or 8.8.8.8.
Wietse
> My wrote on 2026.05.27, at 23:11:20:
> > Hello.
>
> > I didn't even think about possible DNS problem.
>
> > It looks like problem has been fixed in Unbound server:
> > https://wiki.archlinux.org/title/Unbound#First_lookup_fails_after_start
>
> > In my case, I had to increase `max-global-quota` parameter to `500` with
> > some margin. The problem persists even with a value of `300`.
>
> > Thanks!
>
>
> --
> Best regards,
> Lafiel Elentari
> mailto:[email protected] End of PGP section, PGP failed!
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