Postfix illegal address syntax

My postfix install is set up to forward all email going to example.com to my other mail server at mail.example.net. This works fine for all addresses except [email protected] -- the example.com server spits out Illegal address syntax from in the logs and501 5.1.3 Bad recipient address syntax to the client,

How can I tell postfix to forward [email protected] as well? Wikipedia says that ! is valid for the local part.

My configuration is as follows:

main.cf

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
config_directory = /etc/postfix
inet_interfaces = all
mailbox_size_limit = 0
mydestination = mail.example.com, localhost
relay_domains = example.com
myhostname = mail.example.com
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 10.10.10.10/32
myorigin = /etc/mailname
readme_directory = no
recipient_delimiter = +
relayhost =
smtp_header_checks = regexp:/etc/postfix/smtp_header_checks
smtp_tls_fingerprint_digest = sha1
smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_use_tls = yes
transport_maps = hash:/etc/postfix/transport

/etc/aliases

mailer-daemon: postmaster
postmaster: root
nobody: root
hostmaster: root
usenet: root
news: root
webmaster: root
www: root
ftp: root
abuse: root
noc: root
security: root

mime_header_checks

/^Received: (from|by) mail\.example\.net/ IGNORE
/^Message-ID:\s+<(.*?)@mail.example.net>/ REPLACE Message-ID: <[email protected]>

tls_policy

mail.example.net fingerprint
   match=00:01:02:03:04:05:06:07:08:09:10:11:12:13:14:15:16:17:18:19:20

transport

example.com smtp:mail.example.net

Big Warning

Generally including special character like ! or % in the local part of an address is usually a bad idea. Exclamation mark a.k.a ! is a site separator in ancient UUCP addresses. For the safety, you should limit local part of email address to common characters such as [A-Z][a-z][0-9]-.+. It will preserve compatibility across other mailserver in this planet.

However if you insist to use the bang ! to alias, then you may change this parameter value in main.cf

swap_bangpath = no

References: here and here