Change signature in Outlook Web (OWA) with Powershell

Question

Until now, I was using Set-MailboxMessageConfiguration in PowerShell to change OWA's signatures and it worked perfectly. No permission problems, no configuration problems, nothing.

Today, I was trying to update my signature with PowerShell but nothing happened, the signature in the browser is not changed at all.

But if I use Get-MailboxMessageConfiguration, the new signature is there:

I can see that now, it's possible to manage multiples signatures in OWA. But I can't find find any information about that. So, how I can modify the already existing signature? Or, how I can create a new signature?

----- Update 01/11/2021

It's a new feature that is not available for everyone yet. My company's O365 account has it, but my student (also 0365) and classic Outlook account doesn't.

So a third option is: How I can turn off this feature?

----- Update 01/11/2021

Still no defenitive solution. There're some workarounds that may work. Here's the github issue (opened by @Lee) and the Microsoft's Tech Community discussion:

• https://github.com/MicrosoftDocs/office-docs-powershell/issues/8537
• https://techcommunity.microsoft.com/t5/windows-powershell/cant-no-longer-change-owa-s-signature/m-p/2907053

Answer 1

Answering the question relating to your third option "How can I turn off this feature," I opened a support ticket with Microsft for my tenant and they rolled this back for us for now. It took a few weeks to finally get sorted but we can now successfully use this command to set outlook web signatures. Our users no longer see the option to add multiple signatures on the web version.

In the final response, they mentioned that there may be a graph solution in the works for editing the multiple roaming signatures but couldn't offer an ETA.