We are experiecing delay of emails for users because of the Throttlig on Exchange 2013 servers.

This is causing company wide Delay and users are complaining as it takes a lot of time for the queue to get cleared.

We called in Microsoft and they suggested some values changes to msexchangedelivery.exe.config file

We added the following values, but still we face issues when there is Email flood.

Any one faced this or any suggestions that you have.

Hi mdimthyas,

Thank you for your question.

Could you tell more details which throttling was configured on Exchange 2013 in organization?

Could you tell me how long was emails in the queue?

Are there any other issue which could help us troubleshoot.

We could remove the customized  throttling and re-configure it to check if the issue persist.

If there are any questions regarding this issue, please be free to let me know. 

Best Regard,

Jim

Hi Jim,

We are not using any Throttling policies are settings, we did not change those values, left the default.

We have users using some jobs and flooding emails to Exchange servers, with Exchange 2007 we didnt see many issues may be because of different Roles it had, but since we migrated to Exchange 2013 we are seeing that Email queues on the Mailbox servers, sometimes with REcipient reached limit and sometimes Mailbox server thread limit exceeded.

We called in Microsoft and they helpded with changing the values for msexchange.delivery.exe.config file

<add key="MailboxServerThreadLimit" value="120"/>
    <add key="RecipientThreadLimit" value="5"/>
    <add key="MaxMailboxDeliveryPerMdbConnections" value="12"/>

But they said its not recommended, its takes a lot of time to process the changes.

The delay we see varies from 6 hrs to more than that.

This is causing a bottleneck for us as it is being esclated by user community and also Microsoft is not able to provide a viable solution.

Even disabling the Throtlling doesnt work.

We are still discussing with Microsoft on this.

Let me know if any one has seen any issues of this kind with Exchange 2013.

So there's definitely a problem with outbound emails, based on your description of filled mail queues. But do you have this issue with emails received from outside the company ? Are those delivered instantly or it still takes for up to 6 hours for them to be received ?

How do your Exchange servers communicate with the public Internet mail servers ? Do you use a relay service (eg your Exchange servers use a designated smart host for sending) or are your Exchange servers talking directly to the Internet mail servers ?

When you experience the problem, use the Queue Viewer inside Exchange Toolbox to take a look at the queues. Each queue has an "Last Error" field that should provide further data on the issue (eg. connection refused by remote destination, mail loop detected due to exceeded hop count etc)

Another thing that might be the culprit - back pressure. Take a look at the event logs on your Exchange boxes to see if it's the case here. If Exchange detects a shortage of resources, then it will take various measures, including reducing the rate of the mail flow. Check this link.