Can someone please move this to Category: Commvault Q&A, thanks

I have contacted support advised that EWS is the one that’s leveraged

@DanC , glad you were able to get an answer from support!

I’ll move the thread as requested, too.

@Mike Struening thanks

Basically, we will have to make sure both protocols(EWS and Exchange Online Powershell) get re-enabled in order to run exch online mailbox backup when use basic authentication

We were running into an issue where mailbox backup failed to run with basic auth error : 

***CvRTagCreator.log***
0000 0001 10/24 11:41:42 ### $Session = New-PSSession -ConfigurationName "Microsoft.Exchange" -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $Cred -Authentication Basic -AllowRedirection -ErrorAction Stop
0000 0001 10/24 11:41:42 ### Import-PSSession $Session

Connecting to remote server outlook.office365.com failed with the following error message : Access is denied.
***

Though EWS is enabled,  and turned out that  ‘Exchange Online Powershell protocol’ was disabled and it prevent CV powershell script from running. so we followed MS doc and submitted a request to re-enable the service/protocol and it took about 30mins to get it done

Then ran manual discover mailbox from proxy server via Powershell with elevated privilege :

PS C:\Program Files\Commvault\ContentStore\Base> .\AdMailboxMonitor.exe -o autodisover -refreshInterval 0 -a 2 -c 7:O365-MBX -cn Exhange_proxy_server_name  -vm Instance001

once it completes, cv was able to discover all mailboxes and backup starts running
 

https://documentation.commvault.com/2022e/expert/103534_exchange_mailbox_agent_user_mailbox_exchange_online_through_azure_active_directory_environment_port_requirements.html

This link provides the ports.

For Exchange online PowerShell is leveraged to discover users. EWS it for data transfer.

Important note it is recommended to leverage Modern Authentication steps and info listed here:

@Scott Reynolds  thanks

we will switch to modern auth soon
Meanwhile will need to keep  exch backup continue to run under basic auth