At my wits end with crontab/postfix problem

[Alexander Volovics]

I have a small home network connected to the internet via a router/hub.
My internal domain is ever.maas and my external domain is home.nl.

I use postfix and have configured it to mail internally and externally
with /etc/postfix/main.cf, /etc/postfix/aliases, /etc/postfix/sender_canonical
and /etc/postfix/transport (this last to route internal and external mail
through local and smtp respectively).

I only use postfix to mail to the outside world and relay this through
my ISP's smtp mailserver. I use mutt to collect my mail.

If I mail internally as root everything works perfectly (inside the same pc
from 'root' to 'user' of from 'root' to 'root'! I don't need or want to
mail between pc's. The whole configuration is just to enable mail
generated by cron for example to go to 'user').

However if cron mails then 'user' doesn't get the mail but it is relayed to my
ISP's mail server!

Here are two examples.

1) I mail as root:
postfix/pickup[2610]: 26C3F875F: uid=0 from=<root>
postfix/cleanup[2627]: 26C3F875F: message-id=<20040512092700.GC2619 at ik.ever.maas>
postfix/nqmgr[2611]: 26C3F875F: from=<root at ik.ever.maas>, size=405, nrcpt=1 (queue active)
postfix/local[2629]: 26C3F875F: to=<user at ik.ever.maas>, orig_to=<root at ik.ever.maas>, relay=local, delay=0, status=sent (mailbox)

2) Cron mails (as root):
postfix/pickup[2610]: 4256D875F: uid=0 from=<root>
postfix/cleanup[3449]: 4256D875F: message-id=<20040512102033.4256D875F at ik.ever.maas>
postfix/nqmgr[2611]: 4256D875F: from=<root at ik.ever.maas>, size=456, nrcpt=1 (queue active)
postfix/smtp[3450]: 4256D875F: to=<root at home.nl>, orig_to=<root>, relay=mx.home.nl[213.51.128.66], delay=0, status=bounced (host mx.home.nl[213.51.128.66] said: 550 Sender verify failed (in reply to MAIL FROM command))

Why do I get the fork to 'smtp' with cron mail instead of the fork to 'local'.
And why 'orig_to=<root at ik.ever.maas>' versus 'orig_to=<root>'.

(It doesn't make any difference if I enter 'root', 'root at localhost' or
 'root at ik.ever.maas' after MAILTO= in /etc/crontab).

I really would appreciate hints to solve this. I am at my wits end.

Alexander