Why do I notice a delay within Outlook when clicking on the Send/Receive button?
This issue is typically not caused by an issue within the server. The delay can sometimes be caused by a profile corruption within Outlook or a slow internet connection. An addon can also cause the problem.
The first thing that you might want to do is enter safe mode.
If the issue is resolved within safe mode, then the problem is likely related to an addon that you enabled.
Your next step would be to disable any addons.
If the issue continues, then you may want to contact Microsoft support directly.
You may find the following helpful article in regards to resolving the issue with the delay:
You may also want to visit the Microsoft support page: