how to redirect all local system email to an external email address?

My server is with web, dns and ftp on one box and hosted for many virtual domains.
I could found that there are number of email generated by local system

Apr 13 18:13:18 host2 postfix/local[29340]: A0A0C633856F: to=, orig_to=, relay=local, delay=0.45, delays=0.39/0/0/0.05, dsn=5.2.0, status=bounced (can't create user output file) Apr 13 18:13:18 host2 postfix/local[29367]: B52CB633856E: to=, orig_to=, relay=local, delay=0.12, delays=0.05/0.02/0/0.05, dsn=5.2.0, status=bounced (can't create user output file) Apr 13 18:19:12 host2 postfix/local[29696]: 36BF8633856D: to=, relay=local, delay=0.44, delays=0.04/0/0/0.41, dsn=5.2.0, status=bounced (can't create user output file)

host2.myhost.net is the hostname of the machine and not created from virtualmin. So there is no mailbox to received all local system message and this kind of mail log is expected.

Now I want to redirect these local email account to an external email address to read what these emails are about.

How could I do it ?