Everyday users get the below popup when they open outlook
There is a problem with the proxy server’s security certificate
Outlook is unable to connect to the proxy server abl.cab.info (error code 80000000)
This issue is occurring intermittently there is no specific time when any random user would get the pop up.
The error which outlook is reporting could be due to several reasons.
Some are listed below
- Certificate with missing SAN name
- Certificate is not trusted by client
- Certificate is expired
- If there is an incorrect msstd value set or its not matching with the issued to name of your certificate (This issue use to happen in legacy clients like Windows XP etc.)
- Wrong EXCH or EXPR value set – You can check the settings for outlook providers
Run command get-outlookprovider, the msstd setting in the outlook client is picked up by Outlook from this outlook provider values, if it is kept blank the outlook will by default use the hostname you have sent up to connect.
Also the error matters, you need to focus on error code 80000000
The bitmask certificate problem codes are listed in the following table.
Description Error code
Do you have a F5 loadbalancer or any other doing SSL offloading, you need to check this area
Have you checked this technet article ?