Here my /etc/postfix/main.cf

# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
setgrid_group = postdrop
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

myhostname = web4you-gmbh.ch
mynetworks = 192.68.10.0/24, 127.0.0.0/8
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases



# TLS parameters
#smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
#smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
#smtpd_use_tls=yes
#smtpd_tls_session_cache_database = btree:${queue_directory}/smtpd_scache
#smtp_tls_session_cache_database = btree:${queue_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

smtp_helo_required = yes
smtp_client_restrictions = reject_maps.rbl
smtp_helo_restrictions = reject_invalid_hostname,
reject_unknown_hostname,
reject_non_fqdn_hostname

smtpd_sender_restrictions = reject_unknown_sender_domain,
reject_non_fqdn_sender,
reject_rhsbl_sender dsn.rfc-ignorant.org,
permit_mynetworks,
check_sender_access hash:/etc/postfix/access,
check_client_access hash:/etc/postfix/access

smtpd_recipient_restrictions = permit_mynetworks,
reject_unauth_destination,
reject_invalid_hostname,
reject_unknown_hostname,
reject_non_fqdn_sender,
reject_unknown_sender_domain,
reject_non_fqdn_recipient,
reject_unknown_recipient_domain,
check_sender_access hash:/etc/postfix/access,
check_recipient_access hash:/etc/postfix/access,
reject_rbl_client relays.ordb.org,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client list.dsbl.org,
reject_rbl_client sbl.spamhaus.org,
reject_rbl_client dnsbl.antispam.or.id,
reject_rhsbl_client blackhole.securitysage.com,
reject_rhsbl_sender blackhole.securitysage.com,
reject_rhsbl_sender dsn.rfc-ignorant.org,
reject_unverified_sender,

maps_rbl_domains = relays.osirusoft.com,
blackholes.mail-abuse.org,
rbl-plus.mail-abuse.org,
bl.spamcop.net


myorigin = /etc/mailname
mydestination = mail.web4you-gmbh.ch, home.web4you-gmbh.ch,
web4you-gmbh.ch, zarafa-desktop, localhost.localdomain, localhost
relayhost =
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
#mailbox_command = /usr/bin/zarafa-dagent "$USER"
mailbox_command = /usr/bin/procmail -a "$USER"

----------------------------end

and here some log entry's

Jul 18 15:11:03 localhost postfix/smtpd[25223]: connect from
253.7.99-84.rev.gaoland.net[84.99.7.253]
Jul 18 15:11:05 localhost postfix/smtpd[25223]: warning:
253.7.99.84.relays.ordb.org: RBL lookup error: Host or domain name not
found. Name service error for name=253.7.99.84.relays.ordb.org type=A:
Host not found, try again
Jul 18 15:11:25 localhost postfix/smtpd[25223]: warning:
253.7.99.84.dnsbl.antispam.or.id: RBL lookup error: Host or domain name
not found. Name service error for name=253.7.99.84.dnsbl.antispam.or.id
type=A: Host not found, try again
Jul 18 15:11:25 localhost postfix/cleanup[25234]: 8B4ACE1A79:
message-id=<20070718131125.8B4ACE1A79@web4you-gmbh.ch>
Jul 18 15:11:25 localhost postfix/qmgr[4651]: 8B4ACE1A79:
from=<postmaster@web4you-gmbh.ch>, size=263, nrcpt=1 (queue active)
Jul 18 15:11:31 localhost postfix/smtpd[25223]: NOQUEUE: reject: RCPT
from 253.7.99-84.rev.gaoland.net[84.99.7.253]: 450
<juerg.schneider@wandfluh.com>: Sender address rejected: unverified
address: Address verification in progress;
from=<juerg.schneider@wandfluh.com> to=<juerg.schwarz@web4you-gmbh.ch>
proto=ESMTP helo=<253.7.99-84.rev.gaoland.net>
Jul 18 15:11:31 localhost postfix/smtpd[25223]: lost connection after
RCPT from 253.7.99-84.rev.gaoland.net[84.99.7.253]
Jul 18 15:11:31 localhost postfix/smtpd[25223]: disconnect from
253.7.99-84.rev.gaoland.net[84.99.7.253]
Jul 18 15:11:38 localhost postfix/smtp[25235]: 8B4ACE1A79:
to=<juerg.schneider@wandfluh.com>, relay=mail.wandfluh.com[62.2.114.38],
delay=13, status=deliverable (250 Ok)

-----------------END

This looks like an Email that was relayed over my postfix? How to stop
this? There are some more entrys like this.

Juerg