Recently setup Grommunio in my home lab and as part of testing have found most things working successfully. However, have had a repeated problem trying to reply to emails from the Microsoft Mail app. There is no problem with reply to emails via Outlook 2007/2016 or the Grommunio web client.
I have today spent a little time digging into the issue and have deleted/recreated the MS Mail profile/account, repaired the installation, reset the app, uninstalled/rebooted/reinstalled and tested again and get the same result.
I am running the very latest updates (zipper red/up today - not sure how to get all the versions as new to Grommunio and Linux in general) currently in a Proxmox VE 7.2.7 environment but the same was happening in VMWare 6.7.
I have found a possible source of the issue in the Promox Zcore log file. When an email is replied to the log file reports:
[Time date stamp] : I-1334: uid johndoe@somedomain.com tried to send with from=<invalid@invalid>, but no delegate/send as permission.
Any ideas welcomely received. User is currently using either Grommunio web client or Outlook as a workaround as neither of these exhibit the issue. User can compose a new email to the same recipient and that goes without issue from MS Mail app.