Can someone help to figure out what is this error from Exchange 2013 Application Logs. Due to this some user can't login to OWA. Restarting IIS didn't help.

<The number of OWA requests encountering HTTP status code 500 is 796, which exceeds configured acceptable value of 500. Current timestamp: 4/21/2015 6:20:00 AM, Number of errors every minute in the last hour are as follows: 12,19,11,18,13,12,12,13,15,13,2,0,0,12,15,13,11,12,12,12,8,16,14,15,15,28,15,15,14,13,16,15,18,13,12,16,13,12,12,14,14,13,12,12,13,13,17,15,15,22,15,13,11,17,12,16,10,12,12,11,.>

<The number of requests for app pool Owa encountering Http error code &gt;= 400 is now 220, which is less than threshold of 20 percent of total requests in the last hour. Total request count is 1101. History of requests encountering errors in the last hour is: Current timestamp: 4/21/2015 8:03:00 AM, Number of errors every minute in the last hour are as follows: 3,3,4,3,9,3,4,4,6,4,5,3,4,2,3,1,2,3,3,2,2,3,1,2,3,2,2,3,1,4,3,3,2,3,2,3,7,4,4,4,3,10,8,2,3,6,12,4,4,4,5,3,3,2,4,3,3,5,6,1,.>

Thanks,

Uddan

• Edited by Uddan 22 hours 54 minutes ago Additional details

Hi,

Are there any other events related to this issue in application logs? According to this error, I can see that users get HTTP status code 500/400 when trying to log to OWA.

1. For further troubleshooting,  please collect the IIS log.
   On the Exchange 2013 Client Access Server, locate the folder c:\inetpub\logs\logfiles\W3SVC1 (If the IIS log is not enabled, please enable it and try to reproduce this issue.)
2. Check the log files inside the folder and post the related error codes like this(especially the code on the underline).

GET /owa/auth/logon.aspx url=https%3a%2f%2fexc2013cas%2fecp%2f&reason=0 443 - fe80::f90f:9905:3454:d56d%15 Mozilla/4.0+(compatible;+MSIE+9.0;+Windows+NT+6.1;+MSEXCHMON;+ACTIVEMONITORING) - 200 0 0 0

Best Re