Using older versions of Outlook for Mac for personal email and calendar
Hi, Ian Crossley
Good day!
Thank you for posting to Microsoft Community. We are happy to help you.
According to your description, the issue of your concern that relates to Outlook Signatures on your Mac OS Catalina Version 10.15.7
For this issue, since you've tried several attempts and waiting for the Outlook for Mac support team's reply.
Please be kindly to understand that we're Outlook for Windows support that we do not have much resources for test this issue.
Therefore, please give some patience for the professional team's reply.
In addition, have you tried to create a new profile and check if the issue persists? Please give an attempt for Manage profiles or identities in Outlook for Mac.
Meanwhile, we believe Outlook for Mac team are working on this and they will give you further assistance.
Thanks for your time and your understanding would be highly appreciated.
Sincerely,
Alex | Microsoft Community Moderator.