Can't mark email as spam in outlook online mode

Question

We've swtiched one of our users' outlook to online mode since cached mode was a mess-up since turning in-place archiving on for him. It caused all kinds of problem including not being able to search for older emails, ect. Since his outlook is set to online mode, everything works fine, except for one things: He cannot mark any emails as spam. Outlook tells him to switch to cached mode which is absolutely not a possibility for him. Is there any way to make him able to mark spam in online mode?

1. We're talking about an O365 mailbox
2. He's using the installed outlook application on a Windows Server (logged in with RDP as a user)

Answer 1

Hi, the block and allow lists will still work, they will just be stored on the server - meaning they will be accessible to OWA as well.

https://support.microsoft.com/en-us/office/overview-of-the-junk-email-filter-5ae3ea8e-cf41-4fa0-b02a-3b96e21de089

Junk Email Filter differences when Cached Exchange Mode is turned on or off
If you use an Exchange account, you have access to another layer of tools to combat junk email.

If you use Cached Exchange Mode or download to an Outlook data file (.pst) The Junk Email Filter Lists are saved on the server and are available from any computer. The filter lists are also used by the server to evaluate messages. This means that if a sender appears in your Blocked Senders List, then messages from that sender are moved to the Junk Email folder on the server, and they aren’t evaluated by Outlook.

If you work online The Junk Email Filter Lists are saved on the server. They are available from any computer, but only if you have the Junk Email feature enabled in Outlook Web Access or Outlook Web App. The filter lists are also used by the server to evaluate messages. This means that if a sender appears in your Blocked Senders List, then messages from that sender are moved to the Junk Email folder on the server, and they aren’t evaluated by Outlook.

https://www.slipstick.com/outlook/show-dialogs-dismissed-using-dont-show-dialog-setting/

If you want to get rid of that annoying message, try this in the local registry of the machine the user accesses:

https://www.slipstick.com/outlook/show-dialogs-dismissed-using-dont-show-dialog-setting/

Browse to this registry key - replacing the xx with your version number:
HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\Options\General

40 Dialog seen when you work online with an Exchange server account and add an address to the Junk email list:

"The Junk E-mail Filter is not available for your Microsoft Exchange e-mail account because you are working online. To enable the Junk E-mail Filter for this account, switch to Cached Exchange Mode."

Answer 2

@Azazel90

Did that user got an information like below:

Based on my testing, we still could set this sender as a blocked sender:

This setting could also sync to OWA and Exchange server side:

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