cron mail for root going to provider mail server

[Alexander Volovics]

Why is cron generated mail for root being relayed to my
providers smtp server when using postfix?

(At least after configuring postfix's main.cf to account for
 myhostname, mydomain, myorigin and masquerade_domains and using
 mailadress rewriting via sender_canonical_maps)

If I remember correctly this did not happen with the default
sendmail setup.

Was internally generated mail for root even being delivered by
sendmail/postfix/exim in previous redhats before RH9?

Alexander