How to Automate Outlook Signatures with PowerShell in Microsoft 365?

You might have come across it already, but there's this PowerShell script that could help. It was for a similar project I considered (though it never got the green light from management). You could tweak it to pull user info through MS Graph instead of AD. Just remember, if you’re not that confident in editing scripts, you might want to reconsider diving into this kind of solution for the time being.

Another route you could take is to set up a mail flow rule and combine some HTML with user account variables to manage your signatures.

We currently use Exclaimer for our signatures. The admin team looks after the Exclaimer setup while the marketing team takes care of designing the email signature templates.

I’ve actually created a tool called Set-OutlookSignatures specifically for this; it streamlines the process exactly for situations like yours. You might want to check it out!

You can definitely handle it with just PowerShell and Exchange cmdlets, but there are a few catches. You’ll be able to set only one signature (not both for replies and normal messages), and you might need to disable roaming signatures. Make sure to create your template in HTML with any images in base64 format. You can pull the necessary user info from Graph, plug it into your template, and set it up with the `Set-MailboxMessageConfiguration` cmdlet using the `-SignatureHtml` flag. But heads up, this probably won’t work with classic Outlook, only the new one and OWA.

Honestly, I’d recommend CodeTwo for managing signatures. It’s designed specifically for this purpose and functions way better than anything you could script on the client side. Plus, it acts as a transport agent, which gives you a lot more reliability.