When using the EV for Mac Toolbar, messages that were previously archived will show today's date when replied to or forwarded when selecting that action from the EV for Mac Toolbar. If the message is retrieved from archive first by clicking the View button on the EV for Mac Toolbar then the message will show the original date/time in the new message.

In the image above, 1 and 2 show that the date and time of the original message was March 19, 2019 11:45am. When clicking 'Reply','Reply All', or Forward' from the EV for Mac Toolbar we get a new message with the original message in the message body but the date as seen in 3 for the original message is changed to the current date/time instead of showing the date/time for the original message.
When using Outlook 2016 for Mac, select the archived item, click the 'View' button first on the EV for Mac Toolbar, then press 'Reply','ReplyAll', or Forward' button from either an opened message or from EV for Mac Toolbar. Another workaround is to use Outlook 2011 for Mac.
This issue is with MS Outlook 2016. If you are experiencing this issue please create a ticket with Microsoft and then contact Veritas support if needed.