I support a site with numerous iPhones running Outlook against Office 356 email accounts, using Exchange Activesync. We are sporadically seeing errors similar to the one below, when replying to emails. In some cases, users are eventually able to reply after multiple attempts, in other cases they eventually resort to copying and pasting the contents of the email into a new one. We do not use S/MIME, and enabling it in Outlook makes no difference. The object referenced in the error message is just a small graphic that is part of our standard signature block.
We have tried recreating the account, reinstalling Outlook, and even replacing the phone in some instances, however the error keeps recurring, in a seemingly pseudo-random manner.
Were it possible to just disable creation of drafts that may be an acceptable work around, however there seems to be no way of doing this.
The device that threw the error attached was an iPhone 12 Pro Max running iOS 14.4.2
So, and hints on how to further troubleshoot, or disable drafts?