Friday Afternoon Issue - Outlook/Exchange

[ITGURU]

Hello

So this afternoon clients started losing connection to exchange, coming up with the error below.

 

Cannot work out why as nothing is changed during business hours.

I have 2 exchange servers both with Client access role, not clustered, and its only server -001 that it comes up with the error (the server that the mailboxes are on)

 

If you delete the profile in 'mail' from control panel, and re-run outlook the wizard comes up as normal, find the user and creates the account.

 

Can anyone help or point me in the right direction of what to even look for? It's looking for the local server name , but I set all internal/external urls to external DNS domain, and if there is one particular entry which would cause this, which would it be?

[IanT]

https://social.technet.microsoft.com/Forums/exchange/en-US/a30539f3-e1dd-48d5-94a0-accce519f6be/outlook-2010-error-there-is-a-problem-with-the-proxy-servers-security-certificate-error-code?forum=exchangesvrclientslegacy