[quoted text, click to view] > No, it uses a domain name that is resolved. At the moment (after
> installing the DNS server) it works; but why does it need a DNS on
> the local machine, and not simply use the supplied DNS?
[The error that you're seeing refers to the smarthost's A record,
BTW.]
A typical and stable config certainly does not _need_ to have a local
DNS server: lookup of the smarthost's A record can happen over the
wire. You can also use a HOSTS entry or the square-bracketed IP
(though these options mean that you will not be aware of IP changes
from your smarthosting provider).
However, using a remote DNS server across your WAN link -- if that's
what you're doing -- does mean that you are reinjecting latency and
overhead into a setup which is designed to take load _off_ your box.
Depending on your daily mail traffic and client DNS cache, you could
be sending quite a bit of surplus traffic over the wire. In and of
itself, a constant stream of DNS traffic won't cause any problems; but
an increased load means that line errors, firewall/router UDP
processing errors, remote DNS server quotas and stability, etc. will
be more likely to affect you. I don't know which provider's doing your
smarthosting and/or DNS, but I only use smarthosting if forced and
never rely on an ISP's DNS server over my own.
Even if your DNS server was formerly on a different box on your LAN
(rather than across the WAN), same theory holds. SMTP server is using
the same DNS lookups, just against a box that it can reach without
error. You can't trust one-off NSLOOKUPs to tell you how dirty the
connection is; need a sniffer trace for that.
--Sandy
------------------------------------
Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
