LinuxQuestions.org - problem with postfix, inbound mail stuck in queue

Hello all,
I am a newbie... I have installed Ubuntu server 8.0.4 and had no problem with the installation. The web server and webmin work flawlessly.
I also installed Postfix for a mail server. I have a good MX record at my ISP, I can send out through the internet but when I receive mail (internet or local) it just hangs in the queue. In other words it won't delivery it to the mailbox directories for the users.
I have been through my config file several times but being a newbie I can't find my mistake.
could the problem be the mailbox command?
***
copy of my config below
****
# See /usr/share/postfix/main.cf.dist for a commented, more complete version

# 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 = $mydomain
proxy_interfaces = 70.62.40.131
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.

# Uncomment the next line to generate "delayed mail" warnings
delay_warning_time = 1m

readme_directory = no

# 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:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_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.

myhostname = zmail.edisonplus.net
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = $mydomain
mydestination = zmail.edisonplus.net localhost.edisonplus.net localhost edisonplus.net
mynetworks = 172.16.32.0/19; 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_command =
mailbox_size_limit = 1000000
recipient_delimiter = +
swap_bangpath = no
smtpd_recipient_restrictions = permit_mynetworks reject_unauth_destination permit_inet_interfaces permit_sasl_authenticated
home_mailbox = Maildir/