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How can I check email mail flow is passing through Exchange 2010 to exchange 2003?

CTCRM asked
Hi Guys

Lastnight I implemented 2 Exchange 2010 servers each hosting both CAS and Hub Transport Roles on each. I have 2 backend Mailbox servers to implement this evening and all Ex2010 servers will coexist with a single Exchange 2003 server.

I have prepared AD/Schema/Domain, all completed successfully
All Exchange 2010 servers are on Server 2012 boxes, fully updated, hot fixes, and Filter Packs installed, plus all required Features/Roles Enabled
Certificate installed across the Ex platform
CAS & HT roles installed successfully on both 2012 servers (via command line, not GUI)

When I run EMC on one of the new HubCas servers I can see all of the Ex2003 connectors and domain settings, I can also see all of the Mailboxes & Groups.
I got the nightshift to ping emails inbound/outbound to my external mailbox and were received with seconds, and successfully replied to them all.

However, How do I know that the Exchange 2003 Mail Flow is going through the 2 new HubCas servers, and not just passing mail is it was before the new server implementation?
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CTCRMInfrastructure Engineer


I have run the BP Analyser from the Ex2010 server:
Permissions Check 100% OK
Connectivity Check, fine on the 2 new Ex2010, Ex2003 NOT OK
(Communication Port 25 issue)
Server <Ex2003> is a Routing Group Master but a connection to port 25 cannot be established)

My Ex2003 = 10.x.x.x subnet
My Ex2010 = 172.x.x.x subnet
All Exchange related ports enabled on the firewall that splits the two networks, however, Port 25 was not specified in any documentation.

Is TCP Port 25 a required communication port for SMTP traffic between Ex2003 and Ex2010 during coexistence?
Jian An LimSolutions Architect
Top Expert 2016

why exchange 2003 cannot establish port 25?
usually exchange 2003 server smtp port 25 is opened by default

I believe some one have locked down the exchange 2003 at one point.

and of course, port 25 is required for mail relay between hosts.

try to do a simple telnet from exchange 2010 to exchange 2003 on port 25 to ensure you did not get a connect failed.

if yes, then you need to go to exchange 2003 IIS smtp settings to allow additional IP to connect(relay)
ChrisLead Infrastructure Architect

When the mail is delivered just look at the headers and it will show all the hops to get from source to destination
CTCRMInfrastructure Engineer



Thanks for your note. I have received some test emails from the internal LAN out to my mailbox on the Public Domain, and have checked the email header. However, there isn't a mention of any Ex2010 servers, only Ex2003.

I'm not sure whether I should delete and re-create the Ex2003 Virtual SMTP connector as suggested on the Web.
Lead Infrastructure Architect
ok, so that suggests that its not taking any part in the route.
Based on the other info above is the networking between the two all working. You mention that port 25 might not be, can you telnet from one box to the other and vice versa to make sure that they can talk?
CTCRMInfrastructure Engineer


Ex2010 is on a new network (172.x.x.x) and Ex2003 is on our old network (10.x.x.x). Networks have bridged the 2 networks (firewall) opening up all ports as per Microsoft recommendations which online seems to exclude port 25.

When launching Ex2010 EMC I cannot see the Ex2003 server but can see the mailboxes and groups. When originally running the Hub/Case role install onto the first server instead of using the GUI I run the install from PS and therefore didn't get the chance to specify the Ex2003 server, but not sure if I should see the legacy srv in EMC.

So right now I have 2 separate mail environments which to be fair aren't really coexisting. I have also configured the DAG on the 2 MBX servers, when on the MBX servers EMC the DAG looks fine, when I logon to one of the Hub/Cas servers I have a Warning saying: Exchange can't connect to the Information Store service on server EXMBX1. Make sure the service is running.....

Multiple problems here and not sure what it is.
CTCRMInfrastructure Engineer


I ended up having to open up ports 25, 80, 443, 808, 53, 135, 389, 3268, 88, 445, and strangley enough port 1201 to allow me to migrate a mailbox from ex2003 on the 10.x.x.x. to the Ex 2010 platform on 172.x.x.x.

Just sorting out Mail Flow and Mail Gateway Routing now.
CTCRMInfrastructure Engineer


Thanks for your support