Exchange Over a VPN

  • From: "Erhard Haniffa" <erhardhaniffa@xxxxxxxxxxxxxxxxx>
  • To: exchangelist@xxxxxxxxxxxxx
  • Date: Tue, 13 May 2003 07:03:19 -0600

He guys,

I was going over some articles on the MS site in preperation for our
exchange deployment through out our organisation. Just to give you a feel
for what we have planned, I'm going to list out what we are going to do in

We have 4 offices in different parts of canada and the US and they will
all have a minimum of T1's to the internet. The offices will be connected
throuhg VPN's and we planned to have exchange implemented at all the
offices as one organisation with a server sitting at each location.

Then today I say the following on MS. SHould I change the plan to their
recommendation i.e use x400 instead of site connectors?

Site Connector and Message Transfer Agent (MTA) communication within sites
both use RPCs to connect, authenticate, and transfer e-mail messages.
Microsoft does not recommend that you use RPCs over a VPN.

RPC communication requires a minimum bandwidth of 56 Kbps and does not
tolerate latency on the network. As a general guideline, a Site Connector
requires at least 56 Kbps of network bandwidth that is available
exclusively for Exchange Server communications. It must be heavily
stressed that the 56-Kbps transfer rate is a bare minimum for light mail
flow with little or no directory replication traffic. A VPN cannot provide
guaranteed end-to-end bandwidth over a public network, such as the
Internet. Although a VPN connection can be managed over a public network
or over the Internet, the bandwidth is limited to what is currently
available over the current router path. Periodically, latency can be
expected on the network.

Note Site Connectors in a VPN over a public network are not supported. The
options that are supported in a VPN over a public network are:
An X.400 Connector if you are running Exchange Server Enterprise Edition
The Internet Mail Service with connected sites 
Spanning an Exchange Server site across a VPN is also not supported. A
supported configuration is to install or reinstall separate Exchange sites
that are separated by a VPN. To maintain connectivity and reliable mail
flow, Microsoft strongly recommends that you use an X.400 Connector if you
are running Exchange Server Enterprise Edition or the Internet Mail
Service if you are running Exchange Server Standard Edition with connected
sites over a VPN.

If a Site Connector uses a VPN connection, you may have slow or
intermittent mail flow, or it may stop mail flow completely. Event ID
9318, 9316, or 9322 messages may be logged by the Exchange Message
Transfer Agent service in the Application event log. These event ID
messages are also logged if the Site Connector or the MTA communication
within sites spans a VPN. These event ID messages may contain the
following error codes :
1722: This error code indicates that a connection to the RPC server cannot
be made.This may also indicate a possible name resolution problem. Verify
your name resolution as a best effort approach to resolve this error.
1753: This error code indicates that the Endpoint mapper on port 135 is
not responding to a port request.
5: This error indicates that access was denied. To resolve this issue, use
the Override tabs on the Site Connector to verify the account and

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