I recently rediscovered the Set-MailboxMessageConfiguration cmdlet (http://technet.microsoft.com/en-us/library/dd638117.aspx) which can be used with –SignatureHTML or –SignatureText to set a mailbox signature in OWA/ECP. There are plenty of tools out there to do this, my favourite being Exclaimer Signature Manager (http://www.exclaimer.com/products/outlook-email-signatures/outlook-email-signatures.aspx), but hey we can do this for free.
I created a HTML file for each mailbox with the signature and used PowerShell to set them.
$mailboxes = Get-Mailbox
$mailboxes| foreach {$file= "C:\signatures\" + ($_.alias) + ".html"; Set-MailboxMessageConfiguration -identity $_.alias -SignatureHtml "$(Get-Content -Path $file -ReadCount 0)"}
This is useful for me as I have lots of work on with OWA only organisations at the moment. With the Exchange Server 2010 Hosting Edition (multi-tenant) providers may choose to expose Remote PowerShell so a tenant administrator could run this remotely.
I’m planning to expand this further with a simple WYSIWYG editor hosted on SharePoint to allow the Cobweb marketing department to build or upload a template, a service to pull information from AD and update both OWA and Outlook.
It would be cool to see this type functionality making it in to some SharePoint/ECP hybrid in a future Exchange release.