MRS Proxy server not found for mailbox migration to office365

There is 2 MS Exchange on-premise servers, 1 as CAS, and another as hub and MB servers. A hybrid coexistance with Exchange online is formed. However, I logon to the office365 portal, and attempt to migrate any mailbox from on-premise to online always ended with the error as attached.

I did an autodiscover test using MS remote testconnectivy, ended with pass. I also tested that the MRS Proxy server located on the CAS server is enabled. Any thing I missed out? please help to troubleshoot the issue.

Both exchange servers are running with 2010 sp3.

Thanks in advance.
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MichaelBalackAuthor Commented:
Resend the attached
MichaelBalackAuthor Commented:
Look like migration setup tried to look for, but, the CAS server is is a former CAS server, and is already decommissioned.
Hello WorldCommented:

Please run Get-WebServicesVirtualDirectory | FL Identity,MRSProxyEnabled to double check the MRS proxy.
Please pay attention to below link:

Besides, I find an article about How to migrate mailbox data by using the Exchange Admin Center in Office 365, for your reference:

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MichaelBalackAuthor Commented:
Hi Ya Li,

get-webservicesvirtualdirectory shows MRSProxy is enabled. I disabled and then enabled it back still get the same result.
MichaelBalackAuthor Commented:
Hi Ya Li,

Sorry for the delay, being busy with some of the onsite projects.

As for the mrsproxy issue, i have checked with the user, and he told me he did some "improper" modifications that most likely "hay-wire" the settings and eventually yielding such a weird-behaving results.
MichaelBalackAuthor Commented:
Thank Ya Li for the command to check for the status of MRS Proxy service status. Although this info may not lead to the problem solving, at least that is the way to confirm MRS Proxy is indeed operating.

Partly is my mistake as I found out that a lot of settings being "improperly modiified" by the user.
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