Last thursday we learned about an issue introduced with the latest Microsoft Patchday for Microsoft Office 2013, or more specifically KB3172519 (https://support.microsoft.com/en-us/...-april-11-2017). The patch provided through KB3172519 is an unusual one and unfortunately our current approach to restore functionality by adapting the Zarafa compat package, does not seem to provide a way to influence this new behaviour of Outlook. We are still investigating.
The current workaround is to remove this specific update from the workstation to restore the reply-all functionality.
For msi installations:
For C2R installations:
revert back to version 15.0.4911.1002 as described here: https://support.microsoft.com/en-us/help/2770432/how-to-revert-to-an-earlier-version-of-office-2013-or-office-2016-click-to-run
cd “%programfiles%\Microsoft Office 15\ClientX64” (for 64 bits)
cd “%programfiles%\Microsoft Office 15\ClientX64” (for 32 bits)
officec2rclient.exe /update user updatetoversion=15.0.4911.1002