Hi @Leon Batey ,
Based on my search, I found a similar issue to you, it seems that due to the impact of the Outlook roaming signature feature, the signature will now be associated with the email account.
(Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.