Exchange 2007 SP1 - Incoming external mail disappearing

Hello,

I am running Exchange 2007 SP1 on Windows SBS 2008 and it has been running smoothly for several months. Today, however, 2 things (presumably connected) happened:

(1) Incoming messages from external organisations/addresses are seemingly disappearing -- they are not delivered to recipients, and external senders don't get any kind of bounce message. Obviously this is very concerning since I don't know where those messages may have gone. Incoming messages from within the organisation *are* delivered fine, and outgoing messages sent "to the outside world" are also getting through. So it seems to affect only incoming messages from the Internet.

(2) Mobile devices are no longer syncing via ActiveSync properly. It just says "Connecting..." for a while and then eventually gives up. I also allow connections via IMAP, and same thing happens there. Strangely, though, I noticed that my mobile device has synced occasionally from time to time -- after about 2 or 3 hours of it just sitting there, I noticed that as a one-off it did manage to download (internal) messages. When I tried again straight afterwards, it got stuck at "connecting..." again.

I've restarted the whole server and run the Mail Flow Troubleshooter and Best Practices Analyzer. These don't appear to indicate anything different to normal.

The issue with the syncing made me wonder if perhaps the server is being slowed down by some kind of network traffic problem or other resource issue. I'm not aware of anything specific but not really sure how to diagnose these issues. (We are a company of only 4 people and I'm relatively new to Exchange and network admin.)

Thanks for any suggestions anyone has about a fix and/or things to look at!

Mike
MikeBarry09Asked:
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gupnitConnect With a Mentor Commented:
Hi,
Please goto https://www.testexchangeconnectivity.com/ and let me know the results, else the site would lead you to solution
Also read: http://www.nitingupta.in/blogs/index.php/2009/03/27/exchange-server-remote-connectivity-analyzer-video/
Cheers
Nitin Gupta (gupnit)
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MikeBarry09Author Commented:
Hi Nitin,

Thanks -- very useful. When I tried the ActiveSync simulation, the first steps worked fine, but then after a long wait it failed at testing http authentication methods, saying the operation timed out:

Exception Details: Message: The operation has timed out Type: System.Net.WebException Stack Trace: at System.Net.HttpWebRequest.GetResponse() at Microsoft.Exchange.Tools.ExRca.Tests.HttpAuthMethodsTest.PerformTestReally()

When I tried the inbound SMTP test, it failed checking that port 25 was listening/open, specifically giving the detail "The connection was established but a banner was never received".

Given that I've not changed anything in the configuration (and certainly haven't blocked port 25 via the firewall etc.) this seems to be consistent with a very slow Internet connection. A non-technical colleague who is physically on site (I am connecting via Remote Desktop) has reported that "the Internet in general seems extremely slow", so I checked on our ISP's service status page and it seems possible that some upgrade works they are doing could be the root cause. (They didn't bother notifying us in advance, of course.) However, I can currently access Remote Desktop without any noticeable slowness.

Does this behaviour seem consistent with a very slow/intermittent bandwith issue? If so, what will happen to the messages people are trying to send us -- will they just never be delivered, or will the sender's mail server in most cases keep trying to re-send it over a period of time? What concerned me most is that a test message I sent didn't bounce, so a sender may not know that their message couldn't be delivered. That could I guess just be the behaviour of my other ISP's (non-Exchange) mail server?

Thanks,

Mike
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gupnitCommented:
Hi Mike,
I would call upon my Network Engineers to check the Network and devices like Firewall/Router/Switches, along with Bandwitdh tests on ISP. Also disable Internet usage for users and test.
Thanks
Nitin
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Dave_Angel_PortsmouthConnect With a Mentor Commented:
Seams odd that only email is not getting through but you can RDP remotly.

It would be useful to know if incomming emails are unable to get to the server, or, they are arriving and being deleted.

1) Check your MX record, is some external DNS issue preventing external mail from reaching you. (do this from here http://www.mxtoolbox.com/)
2) Are any non-exchange aware virus checkers operating on the exchange server (if so stop them immediatly)
3) Are any of your clients set up to use PST instead of OST files, or indeed any mobile devices not set to leave emails on the server. (try disconnecting all clients and sending emails to the server, add clients one by one)

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