A client of ours was running an in-house Exchange server and decided to move to Office 365... To facilitate the cutover migration, we needed to install a temporary SSL certificate on the server which we bought for a period of three months. We have completed the migration and all of the mailboxes are in the cloud. 

BUT, the certificate has just expired, and when I needed to connect a new Outlook 2013 client to the Office 365 account it comes up with an error saying that the certificate has expired... I've tried to manually set up the account also, but it wont accept the ExchangeID I get when I connect to powershell and run the Get-Mailbox command. It says the server does not exist. 

What is crazy is that if I set up Outlook with very same account from my site (as a test), which has no SSL cert at all, it connects seamlessly. Can anybody give me advice on what approach I might take to resolving this? 

• Edited by JonathanAnon Wednesday, February 18, 2015 11:49 PM

Hi,

If the certificate is expired, please renew your certificate in Exchange server. We can run the following command to get the certificate configuration:

Get-ExchangeCertificate | fl

If the new certificate is generated, please install it in Exchange server and assign it with IIS service. For more information about certificate plan in Office 365, please read:

https://technet.microsoft.com/en-us/library/hh852419.aspx

If you still have any question about certificate installation in Office 365, I suggest you can ask a question in Exchange Online for more suggestion:

https://social.technet.microsoft.com/Forums/msonline/en-US/home?forum=onlineservicesexchange

Regards,