cyrus as trusted user in sendmail

[marc.bigler at day.com]

>Only if sendmail references files owned by the cyrus username.  lmtp
>socket may qualify depending on your setup.

Are there no cases where cyrus itselfs submits messages using directly
/usr/lib/sendmail ? I would like to avoid the warning header "sendmail used
the -f flag to send the from address". How does then Cyrus send it's
auto-generataed failure messages like when there are no mailbox at address
x at y.com ?

Regards
Marc