Mar 06 2017 09:10 AM
Mar 07 2017 02:34 AM
This is common erorr if you do not have the SSL certificate by compelete FQDN of destined client domain/server. Example: server1.contoso.com.
Try fixing the name of the certificates in your environment/office365 connection. Infact you have to improt new certificate from CA authority server in your environment.
Hope this helps you to fix the issue at your IT environement.
Mar 07 2017 06:56 AM
Why would I need a SSL certificate when I'm connecting to outlook.office365.com?
Our Autodiscover CNAME entry for our domain points to autodiscover.office365.com. All of our mailboxes are in Office365, none are on-prem.
Mar 08 2017 01:07 AM
You sometimes see an certificate error when connected to (for example) hotel wifi, whoch terminates ssl connections
Mar 08 2017 05:51 AM - edited Mar 08 2017 06:25 AM
I am assuming you have recently migrated to O365. Please get users to run this O365 diagnostic tool which will pick O365 certificate and create outlook profile. https://diagnostics.outlook.com/#/ if they have O365 valid exchange subscription plans.
Alternatively you can also use this tool for Office 365 Desktop Setup Tool for Office 2010 and Office 2007 https://www.microsoft.com/en-us/download/details.aspx?id=50360
Please let me know if this solves issue.
Mar 08 2017 06:59 AM
No, our email has been in Office365 for 2 1/2 years now.
We haven't seen the error since it first occurred so I'm going to pressume it was a temporary error on the server side.
Mar 08 2017 07:21 AM
Up to you but would recommend to get users with older version of outlook to run this tool to get latest updates from 365. https://www.microsoft.com/en-us/download/details.aspx?id=50360
Been O365 Support Engineer, we had few customers having issues.
Mar 29 2017 10:47 AM
We had a DNS server (small-office router actually) apparently corrupting DNS lookups – I suspect because the record Office 365 returns is rather large, what with multiple addresses and IPv6 addresses. Outlook was presumably thus sent to an adjacent server in the Microsoft server farm. Certificate errors was the error there. It would be interesting to see what server names were allowed by the certificate.
Apr 03 2017 01:10 AM
Looks like a proxy certificate issue. Especially, if users connect to internal source (e.g. SharePoint) and Office 365 using Outlook.
Apr 04 2017 09:46 AM
We have a couple of clients with this error. They have two different Internet Service PRoviders, one active and one of backup. Booth customers had the same ISP active, we change to the backup ISP for all out connections.
We check DNS, SPN, outlook´s updates, etc..
The issue was fixed changing the ISP .
Apr 04 2017 06:12 PM