Redmine

My rspamd scanner reports for the account registration notification the following symbol:
Symbol: XAW_SERVICE_ACCT(1.00)

which is triggered by this header:
X-Authentication-Warning: Ubuntu-2004-focal-64-minimal: www-data set sender to noreply@redmine.org 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.
https://forum.howtoforge.com/threads/fix-for-x-authentication-warning.18269/

I know a few things about email, so if I can assist any further with this issue, let me know!