Re: Problem sending email out of Exchange 2003
- From: "SuperGumby [SBS MVP]" <not@xxxxxxxxxxx>
- Date: Fri, 10 Oct 2008 08:52:55 +1100
Synchronicity, or just plain coincidence?
For the last couple of days I have been fighting with Exchange showing
similar behaviour. A client had moved offices, changing ISP in the process.
Sortta similar hey?
Here's a curious part of it. 6wks ago they moved from their original
location to temporary offices, again with a change of ISP. No problem
appeared at this time.
Original lcation - ISP1.
Temp location - ISP2.
Final location - ISP3.
I had inherited support of this system ~2.5yrs ago, the initial install
having been performed by a 'corporate admin' type person, not familiar with
SBS.
My problem was resolved last night when it was found that Exchange was not
referring DNS queries to SBS but instead had been given specific DNS
servers, those of ISP1, in the SMTP server. Seems that when SBS was moved to
ISP2 these ISP1 servers were still available but when connected to ISP3
Exchange SMTP was no longer able to query these servers. (this sounds like
your basic problem, concerning your fallback between TWC and Covad)
How do we avoid it? By _not_ telling Exchange SMTP to refer to an external
server (this is the default condition) and by using a DNS query mechanism
which is available from both ISPs.
On SBS, the CEICW prompts for 'DNS servers' as part of the network setup.
Leaving the entries blank is a valid choice, causing SBS DNS to use 'root
hints', the internet 'root servers', for DNS resolution. This effectively
'disconnects' SBS DNS from any external service (ISP).
An alernative, with benefits concerning 'internet abuse', is to specify the
OpenDNS servers during the network setup portion of the CEICW, this causes
SBS to use OpenDNS as 'DNS Forwarders' and the OpenDNS DNS servers _should_
be available from any internet connection.
"Andrew B. Abrams" <AndrewBAbrams@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:0E04490D-39E3-4F20-9773-F64BE7FF562A@xxxxxxxxxxxxxxxx
All of a sudden, I cannot send email out of Exchange using DNS to send
directly from the SMTP server. When I look at the SMTP Queue, it is just
jammed with emails it is re-trying to deliver. I use Time Warner Cable
Business Class Road Runner and haven't had this issue before. If I setup
the
SMTP connector to smtp-server.wi.rr.com, then email goes out as it is
relaying through TWC. This is ok, but I prefer not to use a connector if
I
don't have to. The main reason is we have a failover Internt to Covad
DSL.
If the TWC is down, and we are on failover, then I cannot even relay to
TWC's
SMTP servers as they block the relay from the Covad IP block (or Covad is
blocking us from getting to TWC)
TWC says they aren't blocking us on Port 25 nor is our domain nor IP block
in any block lists.
Is there anywhere I can look, or things I can test, to see why I cannot
send
email from Exchange via DNS rather than using the SMTP connector?
.
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