@chris.smearing If you switch from Apache to nginx (or start a new site with the default of nginx instead of Apache), does Mailpit then catch all emails for you?
You can switch existing sites from the “overview” pane: select “nginx” from the “web server” dropdown and click “Apply”.
I’m looking into why it’s only failing on Apache under Windows, but I hope this helps as a workaround for now. (I appreciate that you might not want to switch to nginx permanently.)