Periodic EWS Response Delay(Time out).

Hellow.

Problems are occurring while using EWS.

basic authentication is being used.

Below is part of the code.

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service.Credentials = new WebCredentials("adminAddress", "adminPassword");
service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, "userAddress");
service.HttpHeaders.Add("X-AnchorMailbox", "userAddress");

service.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");

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There is usually no problem.

However, the EWS response time is always delayed at 5 p.m. in Korean time.

After 10 minutes, the response speed returns to normal.

It is believed to have lasted more than 3 months.

What is the cause of this phenomenon?

Is there a case where the same phenomenon occurred?