sieve redirect to foreign email gets “Relay access denied”

I have a postfix mail server with sql authentication and I want to implement sieve on it.

Sieve is working relative good, rules who contain 'fileinto' are executed perfectly. The problem is the redirect to other servers. I configured a rule in Sieve to redirect any email containing "redirect" in subject to a specified foreign destination. # So practically a email coming from sender@live.de for the local user testuser@server.net should be redirected to destination@gmail.com when the subject contains "redirect"

if header :contains ["subject"] ["redirect"] {redirect
"destination@gmail.com"; stop;}

when I test it I get the following log entry

/postfix/smtpd[32114]: NOQUEUE: reject: RCPT from
mail.server.net[xx.xx.xx.xx]: 554 5.7.1 <destination@gmail.com>:
Relay access denied; from=<sender@live.de>
to=<destination@gmail.com> proto=ESMTP helo=<mail.server.net>/

How can I tell postfix to let dovecot/sieve relay the email?

can somebody give a hint?

postconf -n

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
broken_sasl_auth_clients = yes
config_directory = /etc/postfix
content_filter = smtp-amavis:[127.0.0.1]:10024
default_process_limit = 15
disable_vrfy_command = yes
dovecot_destination_recipient_limit = 1
home_mailbox = mail/
inet_interfaces = all
mailbox_size_limit = 0
mydestination = mail.server.net, localhost
myhostname = mail.server.net
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
myorigin = /etc/mailname
readme_directory = no
recipient_delimiter = +
smtp_tls_note_starttls_offer = yes
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtp_use_tls = yes
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_helo_restrictions = reject_unknown_helo_hostname
smtpd_recipient_restrictions = permit_sasl_authenticated,
reject_unknown_sender_domain,
reject_unknown_reverse_client_hostname,
reject_unknown_recipient_domain, reject_unverified_recipient,
reject_unauth_destination, reject_rbl_client zen.spamhaus.org,
reject_rhsbl_helo dbl.spamhaus.org, reject_rhsbl_sender
dbl.spamhaus.org, check_policy_service inet:127.0.0.1:10023
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_path = private/auth
smtpd_sasl_security_options = noanonymous
smtpd_sasl_type = dovecot
smtpd_sender_restrictions = permit_sasl_authenticated,
permit_mynetworks, reject_authenticated_sender_login_mismatch,
reject_unknown_sender_domain
smtpd_tls_auth_only = no
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_loglevel = 2
smtpd_tls_received_header = yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_use_tls = yes
soft_bounce = no
virtual_alias_domains =
mysql:/etc/postfix/mysql_virtual_alias_domains.cf
virtual_alias_maps = mysql:/etc/postfix/mysql_virtual_alias_maps.cf
virtual_mailbox_base = /var/vmail
virtual_mailbox_domains =
mysql:/etc/postfix/mysql_virtual_domains_maps.cf
virtual_mailbox_limit = 512000000
virtual_mailbox_maps = mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf
virtual_transport = dovecot

dovecot -n

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-amd64 x86_64 Debian 7.6
auth_debug_passwords = yes
auth_mechanisms = plain login
auth_verbose = yes
auth_verbose_passwords = plain
debug_log_path = /var/log/dovecot/dovecot.debug.log
disable_plaintext_auth = no
first_valid_gid = 99
first_valid_uid = 99
hostname = maxi.zp1.net
info_log_path = /var/log/mail.info
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
listen = xxx.xxx.xxx.xxx
log_path = /var/log/dovecot/dovecot.log
login_greeting = Dovecot ready, Sir.
mail_debug = yes
mail_gid = 99
mail_location = maildir:~/mail:LAYOUT=fs:INBOX=/var/vmail/%u/mail/
mail_plugins = acl
mail_uid = 99
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope
encoded-character vacation subaddress comparator-i;ascii-numeric
relational regex imap4flags copy include variables body enotify
environment mailbox date ihave
namespace {
   location = maildir:/var/mail/public
   prefix = Public/
   separator = /
   subscriptions = no
   type = public
}
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     special_use = \Trash
   }
   prefix =
   type = private
}
passdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
plugin {
   acl = vfile
   acl_anyone = allow
   acl_shared_dict = file:/var/lib/dovecot/shared-mailboxes
   mail_log_events = delete undelete expunge copy mailbox_delete
mailbox_rename
   mail_log_fields = uid box from subject msgid size
   sieve = ~/.dovecot.sieve
   sieve_default = /var/lib/dovecot/sieve/default.sieve
   sieve_dir = ~/sieve
   sieve_global_dir = /var/lib/dovecot/sieve/global/
   sieve_max_actions = 64
   sieve_user_log = ~/.dovecot.sieve.log
}
postmaster_address = root@server.net
protocols = " imap sieve pop3"
service auth {
   unix_listener /var/spool/postfix/private/auth {
     mode = 0666
   }
   unix_listener auth-userdb {
     group = postfix
     mode = 0666
     user = postfix
   }
}
service managesieve-login {
   inet_listener sieve {
     port = 4190
   }
   service_count = 1
}
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.pem
submission_host = smtp.server.net
userdb {
   args = uid=vmail gid=vmail home=/var/vmail/%u
   driver = static
}
verbose_proctitle = yes
protocol lda {
   mail_plugins = acl sieve
}
protocol imap {
   mail_plugins = acl autocreate acl imap_acl
}
protocol sieve {
   mail_max_userip_connections = 10
}