Mails Not Dropping

Hello guys,

Please I am new to Exchange Administration.

we can not receive mails from outside domain , however we can send mails in and outside domains.

Please what could be the cause of this, because this is the second time it will be happening in the last 15-days and how do I resolve this once and for all?

Please note that there is no error at all.

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Simon Butler (Sembee)ConsultantCommented:
It is unlikely that there  is no error - Exchange is very noisy when problems occur.
I expect the issue is due to disk space on the C drive - if it drops below a certain level Exchange will stop processing email externally and then eventually internally as well.

Scott CSenior EngineerCommented:
Look in the application log for backpressure events.  15004, 15005, or 15006.  You are most likely running into a disk space issue.

If you are below 5 gig, this can cause what you are describing.  Look in your IIS logs and see if some of those can be purged or moved.  Also empty recycle bin, temp folders etc to free up disk space if needed.

Follow the steps in this blog for disk cleanup steps.

After disk space has been freed up, restart the Transport Service.  This should get mail flowing again.  Otherwise, it should start flowing after about 15 minutes.
Scott CSenior EngineerCommented:
One more thing.  Wherever the mail is coming through, if it isn't being spooled before it hits Exchange, some of those messages may be gone for good.  If they were being spooled, you should be ok.
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HafeezAzeezAuthor Commented:
Hello Simon and ScottCha,

I truly appreciate your swift response.

The problem is not backpressure/disk space, because I still have up to 440gb on the server.

However, I restarted the server and  outside mails dropped, which left me wondering what could be the cause, how to prevent/rectify it.

Because of this same issue, the exchange 2010 was upgraded SP3 the other time it happened.

Scott CSenior EngineerCommented:
My guess is that a simple restart of the Transport Service may have resolved the issue.  After the upgrade, was the server rebooted?

I have seen many times where updates were applied, the server not rebooted, and strange things happen until the reboot.

As the server is no longer in state, we can't know for sure.

However, I have seen it be a best practice to reboot after any and all updates are applied, especially OS altering ones.

Also make sure you are running the latest RU for Exchange.  There have been many RUs since SP3 came out.

Current RU for Exchange 2010 is RU10, if you are just at SP3, you are over 3 years out of date.
HafeezAzeezAuthor Commented:

After the update,the server rebooted fine with no issues.

I have the most current RU10 which was release in June 2015.

Scott CSenior EngineerCommented:
Then my suggestion is if/when this happens again, Look at the event viewer and see if there are any Exchange Transport events and make note of these.

After looking through them, restart the transport service and see if mailflow starts up.  I've seen it a few times where something in the transport service is just locked up and there are no events logged but a restart corrects the issue.

I, myself, ran into this on two occasions I can remember working for MS as an Exchange engineer where restarting the service fixed the issue, but there were no events logged.  It's not common, but it does happen.

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Scott CSenior EngineerCommented:
Glad to have helped.  Remember, gather as much information as you can when the system is in state because once you get mail flowing again, no new data will be gathered until the issue happens again.  This is true for most issues.
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