Lookup table ignored for users sending mail from the localhost

Hi,

I am running Postfix 2.10 /w Cryus-Imapd and Squirrelmail. I am having
a problem with users that are sending mail via Squirrelmail
(localhost... running on the same system as Postfix). It ignores the
local user lookup table for them. So if I send a message to "user"
instead of "user@domain.tld" the message gets delivered to "user" on the
localhost, regardless if that user exists or not. (With Cyrus and the
autocreateinbox flag it creates the inbox and places the mail there.) If
you try to send a message to "user" from any other system that's not
localhost.. it tells you the mailbox/user doesn't exist as I would
expect to happen. This is probably correct functionality... but it
creates a problem. If one of my users sends a message via web mail to
"Bob", thinking autocomplete is going to work like it does in Outlook,
or they type the wrong email address... it delivers the email on
localhost and my user is oblivious to the fact the other person didn't
get the message.

How would I go about changing this? All my users are virtual users
stored in a MySQL table with the exception of root's email.

Here is the output of "postconf -n"

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
allow_percent_hack = no
append_dot_mydomain = no
bounce_size_limit = 20971520
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
header_checks = regexp:/etc/postfix/header_checks
html_directory = no
mailbox_transport = cyrus
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 20971520
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain,
mysql:/etc/postfix/mysql-mydestination.cf
myhostname = mail.xxxxxxxxxxxxxxxxx.com
mynetworks = 209.250.113.64/26, $mydestination
newaliases_path = /usr/bin/newaliases.postfix
readme_directory = /usr/share/doc/postfix-2.1.5/README_FILES
sample_directory = /usr/share/doc/postfix-2.1.5/samples
sender_canonical_maps = mysql:/etc/postfix/mysql-canonical.cf
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtpd_recipient_restrictions = permit_sasl_authenticated,
permit_mynetworks, reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain =
smtpd_sasl_security_options = noanonymous
swap_bangpath = no
unknown_local_recipient_reject_code = 550
virtual_alias_maps = mysql:/etc/postfix/mysql-virtual.cf