Hey everyone..I really need your help.. I setup postfix as a null client on my VPS to send only automated, outbound emails. I also have Google App mail for the domain (for sending receiving personalized emails), however, I receive the following in Gmail for emails sent by from Postfix. The destination email address are correct (tried a few of my personal email addresses). I once got Postfix to work, but no longer the case.

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host ASPMX.L.GOOGLE.com[209.85.223.16] said:
550-5.1.1 The email account that you tried to reach does not exist. Please
try 550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1

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*** where you see EXAMPLE.com, my real domain is used.

"postconf -n" outputs

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = loopback-only
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost
mydomain = example.com
myhostname = mail.example.com
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES
relayhost = $mydomain
sample_directory = /usr/share/doc/postfix-2.3.3/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550

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According to POSTFIX, a null client setup should follow:

1 /etc/postfix/main.cf:
2 myorigin = $mydomain
3 relayhost = $mydomain
4 inet_interfaces = loopback-only
5 local_transport = error:local delivery is disabled
6
7 /etc/postfix/master.cf:
8 Comment out the local delivery agent entry

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Furthermore, I have DNS "A" record for mail.example.com that points to my IP address. My IP address is also listed in the SPF record.

WHAT AM I DOING WRONG?

What do your mail logs say?

It says basically the same as google:
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Apr 11 23:46:59 hostname postfix/smtp[17965]: 5C3961D84B5: to=<user@domain.com>, relay=ASPMX.L.GOOGLE.com[209.85.223.16]:25, delay=3.3, delays=0.02/0.01/0.23/3, dsn=5.1.1, status=bounced (host ASPMX.L.GOOGLE.com[209.85.223.16] said: 550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 http://mail.google.com/support/bin/a...py?answer=6596 15si15905946iwn.6 (in reply to RCPT TO command))
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The same reject occurred for another user and a few personal accounts I have.

I dabbled with the settings, and Postfix is now working. "relayhost = $mydomain" is no longer set in the latest settings. Could that be the cause? According to the guide, relayhost is supposed to be set. Here's the latest config output:

[root@hostname log]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = loopback-only
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost
mydomain = example.com
myhostname = mail.example.com
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES
sample_directory = /usr/share/doc/postfix-2.3.3/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550

Just wondering if anyone could confirm if "relayhost = $mydomain" should have made a difference, especially if not what was recommended.