Hi @ Muhammad Yousuf Ansari,
- Since you are using a third-party product(EM client), kindly note that we may not be very familiar with it. If possible please also contact their support for help.
- Check the headers of delayed messages and see where messages are delayed. Plug the headers into: https://mha.azurewebsites.net/.
- You can use the get-queue command to see if there are a large number of mails stuck in the queue, or use the queue viewer to check if there is a problem.
- Check backpressure to see if there is enough disk space on the drive.
For details about back pressure, you can read this article: Understanding back pressure.
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