Stan Hoeppner:
> Wietse Venema put forth on 12/1/2009 3:47 PM:
>
> > Surely, mail is injected via SMTP, and therefore, the Postfix SMTP
> > server will attempt to lookup the client hostname and IP address;
> > since they are using SMTP-based content filters, that is another
> > source of name service lookups. All this presents a load on name
> > service. I have seen enough to know that a bad DNS configuration
> > can do wonders for performance.
>
> Assuming the test streams are generated by a handful of SPECmail load
> generator hosts, the hostnames and addresses of those client machines
> would quickly be cached, no?
I can assure you that there is no such caching the Postfix SMTP
server before the SMTP-based content filter, and not in the Postfix
SMTP server after the SMTP-based content filter. In addition, Postfix
and content filters may do other DNS lookups for reputation etc.
Ideally, name/address/reputation lookups will have only minimal
impact, but I was explicitly not talking about ideal configurations
when I wrote:
If your performance is inadequate, I suggest that you do a detailed
system performance analysis to find out if the limit is CPU,
memory, file I/O or perhaps some trivial DNS configuration problem.
I would not be so quick to dismiss DNS-related problems out of hand
in scenarios that involve synthetic email messages.
Wietse
