Email Notifications: offending header
My rspamd scanner reports for the account registration notification the following symbol:
which is triggered by this header:
X-Authentication-Warning: Ubuntu-2004-focal-64-minimal: www-data set sender to email@example.com using -f
I’m not sure what MTA that server is using, but it looks like sendmail‽
To prevent this header from being added, it seems you would have to add www-data to the trusted-users list, see e.g.
I know a few things about email, so if I can assist any further with this issue, let me know!