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Microsoft Exchange


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#1 aujus3

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Posted 09 February 2011 - 04:27 PM

Hello,

I read your forums once in a while when I'm stuck and can usually find an answer. Well, I have a unique situation and need to consult as many gurus as possible for help.

I work for a non-profit publishing company (that I'll call NPP for this post) who is vaguely affiliated with a major private university (that I'll call MU for this post).

In computing and networking terms, we are basically a separate entity. We have our own in-house IT department which consists of my manager and myself (as his part-time assistant). The only networking affiliation we have w/ MU is that we get one IP address from them (they're physically across the street from us), which we split into about 45+ internal static IPs (I think they're called NAT'd IPs, but I'm far from a networking expert). We have no wired DHCP server (or DHCP is disabled completely). The wireless network we have is on a Linux server and will only connect PCs which have had their MAC addresses registered on the server by myself or my boss. Also, the wireless network is protected by a key which has not been given out to anyone besides my boss and myself. In other words, the odds of a computer or other device that wasn't issued by NPP connecting to any part of our network is nearly impossible.

The other tie we have to MU is that we use their MS Exchange email servers for our email.

Recently (for the past month or so) we've seen unpredictable disconnections between Outlook 2003 and Eudora clients (yes, we're non-profit and so necessarily we're cheap dinosaurs). At the exact same time, and irrespective of which computer happens to disconnect from the MS Exchange server, we are immediately unable to connect to MU's Outlook Web Access (OWA) service from ANY computer in our NPP building, regardless of whether or not it's the computer that has lost connection to the Exchange server in its email client.

Eventually (sometimes within a couple minutes, sometimes within a couple hours, or sometimes after a full day/night) the email client (Outlook or Eudora) reconnects automatically to the MS Exchange server (without having to re-enter MU server login credentials) and all is well, at least in the email clients. Eventually the OWA web site starts working again too. Like I said, the connection issues are hit and miss.

The only coincidences I've been able to pin down are that the disconnections don't start happening until about 9:30 or 10:00 a.m. each day (but once they've started, there doesn't seem to be any predictability whatsoever to the dropped connections), and as soon as one or several email client(s) disconnect(s), OWA stops loading properly for everyone in the building, at least temporarily.

My manager and I have been in contact with MU's networking and email staff trying to pin down what the problem might be, but we haven't had any luck at all yet.

Can anyone give me any guidance (and please bear in mind that I am NOT a networking guy, at least not yet, so many of the terms are foreign to me). If you have any specific questions that might help you figure it out, please don't hesitate to ask.

In advance, thank you!

Edited by aujus3, 09 February 2011 - 05:10 PM.


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#2 MBakerNH

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Posted 14 February 2011 - 12:13 PM

There are SO many places to start. Since you are connecting to a foreign (to your network) hosted email, you need to be sure that the network over there is OK (so you need to hear back from MU.) If you can still connect to the internet during the outages, then it is even MORE likely that the problem is external to NPP. If I were troubleshooting this, I would have MU look at the logs of their inbound router (they may have QoS settings that throttle down traffic, and they may be booting you off, as you are NPP not MU) and their Exchange server logs (perhaps authentication is timing out when LPP tries to hit the server.) Since the credentials are cached locally, it's no surprise that you don't have to log back in to the server.

If the internet is working during these outages, if all other WAN/LAN traffic is fine, you are at the mercy of MU staff to check on their end, as it is almost guaranteed to be a problem there, not with you.

If the connection to MU is through a VPN connection (and it most likely is,) you could look at your router logs when this occurs, and see if there's a clue on your end (for example, if you are both using Aggressive mode authentication, which is more prone to dropping, then you might have some ammo to go to them with for help.) The problem with that is that the logs are fairly arcane, so if you are not a networking guy, they might prove an insurmountable challenge.

#3 aujus3

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Posted 14 February 2011 - 03:32 PM

MBakerNH,

Thank you for the advice and thoughts. You've helped us come closer to confirming what we suspected.

Since I posted this, We've done experiments now where we find one person whose Outlook client won't connect to MU (or, has disconnected), then find someone whose client IS connected. We then disconnect the connected person via closing Outlook, and voila! The person who wasn't connected becomes connected. We've experienced this same phenomenon in about 5 separate cases now, each time with different sets of users.

I have informed MU's IT department of this fact (on 2/10/11), but they have not updated our incident notes yet, so I'm guessing they either haven't been working on it or haven't found the problem.

If any new ideas come to mind in light of this information I'd love to hear about them; otherwise we'll keep pressuring MU's IT dept. for results. Again, thank you kindly for your help.

#4 aujus3

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Posted 14 February 2011 - 04:27 PM

Something just occurred to me about this issue...

I'm going from memory here, so could be remembering wrong, but it seems like the beginnings of these connection problems roughly coincide with the fact that we (my manager and I) set up an internal email client on an old Mac Mini running Linux (Ubuntu v. 10.10). This mail server has about 15 mailboxes on it that have been added to about 10 different Outlook 2003 clients using IMAP settings.

Is it possible that our internal email server is somehow screwing with our connections to MU's MS Exchange client, causing this whack-a-mole effect?

Edited by aujus3, 14 February 2011 - 04:28 PM.


#5 MBakerNH

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Posted 18 February 2011 - 08:28 PM

Your mixing up your terms... did you set up an email client or server? I think you set up a server.

I suppose it's possible that it's the root cause, but it seems unlikely, although the test is easy enough. This problem occurs every day? Shut down those 10 users for a day, by shutting down the Mac/Linux machine. If you see no errors, you've identified the culprit.

I assume the accounts are under a different domain? If not, how does the internet know to send those 15 accounts to you, as opposed to MU? And if you are pulling those 15 accounts directly off of the MU server - why are you using an intermediary server?

Again, the theory is easily tested. Shut the beast down, if that's the problem, et viola.

"Since I posted this, We've done experiments now where we find one person whose Outlook client won't connect to MU (or, has disconnected), then find someone whose client IS connected. We then disconnect the connected person via closing Outlook, and voila! The person who wasn't connected becomes connected. We've experienced this same phenomenon in about 5 separate cases now, each time with different sets of users."

This sounds almost more like a licensing issue, though, again, that's MU's bailiwick.

#6 aujus3

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Posted 21 February 2011 - 08:19 AM

I did misspeak. It's an internal email server, not a client (I know the difference, I just typed that up in too much of a hurry, hehe, sorry), and yes it's under a different domain, not associated with MU in any way except that the machine it's on uses a NAT'd IP like the rest of the machines at NPP.

My manager, who has final say on what we test here, is convinced (as you seem to be) that the problem is on MU's side and they need to devise a solution for us. Their exchange server admin has contacted us and said they suspect it's their firewall that's seeing over x amount of connections to the exchange server at once as a security threat and it so it starts cutting off the connections after a certain point. That's what my manager said it was from day one, to his credit.

I'll present the 'shut down the Linux email server' idea to the boss soon and see if he wants to try it, even though it seems an unlikely culprit.

Again, thank you much. :)




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