Hello Anthony Del Buono,
I understand that Copilot has recently started appearing when you compose or reply to emails in Outlook on the web and Mac.
Copilot is included with Microsoft 365 Premium and can appear as part of Outlook’s email drafting experience.
Just to clarify, are you looking to disable/hide Copilot when composing emails, or are you mainly asking why it has recently started appearing?
Once you confirm, I can point you in the right direction.