How to setup DNS behind Airport Extreme and ISP that will not reverse DNS

Question

Hi,
I am having issues setting up my Mac Mini with SLS. Right now my server is connected to the internet through my Airport Express. It gets a static address from the router (10.0.1.13). The router also has a static address from my ISP. I own the domain redcedarpoint.com. I have set the A record to point to my static router IP address. I also setup a CNAME for server.redcedarpoint.com to the same address.
During the initial portion of setup SLS sees my ISP's domain versus my own domain and incorrectly fills the local domain name. I manually changed these to redcedarpoint.com and called the server 'server'. This puts server.redcedarpoint.com into all the host names. Everything seems to work, but now all my users get email addresses like [email protected] versus [email protected]. I have manually set mail host name to redcedarpoint.com (although this is wrong I think). It solves the email addressing issue, but now postfix gives me a warning about a duplicate:
+Jan 27 21:20:45 server postfix/postmap[70670]: warning: /var/amavis/local_domains.db: duplicate entry: "redcedarpoint.com"+
My question is: What should I fill in during setup and how should I setup DNS from my hosting service.
By the way, I am also trying to funnel all inbound and outbound email through my premium Google Apps subscription.
Here's also the result of postconf -n
+Last login: Wed Jan 27 21:19:47 on ttys000+
+server:~ ianknight$ postconf -n+
+biff = no+
+command_directory = /usr/sbin+
+config_directory = /etc/postfix+
+content_filter = smtp-amavis:[127.0.0.1]:10024+
+daemon_directory = /usr/libexec/postfix+
+debugpeerlevel = 2+
+enableserveroptions = yes+
+header_checks = pcre:/etc/postfix/customheaderchecks+
+html_directory = /usr/share/doc/postfix/html+
+inet_interfaces = all+
+mail_owner = _postfix+
+mailboxsizelimit = 0+
+mailbox_transport = dovecot+
+mailq_path = /usr/bin/mailq+
+manpage_directory = /usr/share/man+
+mapsrbldomains =+
+messagesizelimit = 10485760+
+mydestination = $myhostname, localhost.$mydomain, localhost, dmcwatering.com, internationalcardio.com+
+mydomain = redcedarpoint.com+
+mydomain_fallback = localhost+
+myhostname = redcedarpoint.com+
+mynetworks = 127.0.0.0/8,216.239.32.0/19,64.233.160.0/19,66.249.80.0/20,72.14.192.0/18,209.8 5.128.0/17,66.102.0.0/20,74.125.0.0/16,64.18.0.0/20,207.126.144.0/20,173.194.0.0 /16+
+newaliases_path = /usr/bin/newaliases+
+queue_directory = /private/var/spool/postfix+
+readme_directory = /usr/share/doc/postfix+
+recipient_delimiter = ++
+relayhost =+
+sample_directory = /usr/share/doc/postfix/examples+
+sendmail_path = /usr/sbin/sendmail+
+setgid_group = _postdrop+
+smtpsasl_authenable = yes+
+smtpsasl_passwordmaps = hash:/etc/postfix/sasl/passwd+
+smtpdclientrestrictions = permit_mynetworks permitsaslauthenticated rejectrblclient zen.spamhaus.org permit+
+smtpdenforcetls = no+
+smtpdhelorequired = yes+
+smtpdhelorestrictions = rejectinvalid_helohostname rejectnon_fqdn_helohostname+
+smtpdpw_server_securityoptions = cram-md5,gssapi,login+
+smtpdrecipientrestrictions = permitsaslauthenticated permit_mynetworks rejectunauthdestination checkpolicyservice unix:private/policy permit+
+smtpdsasl_authenable = yes+
+smtpdtlsCAfile =+
+smtpdtls_certfile =+
+smtpdtls_excludeciphers = SSLv2, aNULL, ADH, eNULL+
+smtpdtls_keyfile =+
+smtpdtlsloglevel = 0+
+smtpduse_pwserver = yes+
+smtpdusetls = no+
+unknownlocal_recipient_rejectcode = 550+
+virtualaliasmaps =+
+server:~ ianknight$+

Answer 1

The first one is easy...
Jan 27 21:20:45 server postfix/postmap70670: warning: /var/amavis/local_domains.db: duplicate entry: "redcedarpoint.com"
You have redcedarpoint.com set as both the domain name and the hostname of the server. That is not correct:
mydomain = redcedarpoint.com
myhostname = redcedarpoint.com
In this case, myhostname should be the reverse DNS hostname that the recipient mail server would see on outgoing mail - typically this would be something like 'mail.redcedarpoint.com
You should also fix the mydestination parameter so that it includes your domain name as well:
mydestination = $myhostname, localhost.$mydomain, localhost, dmcwatering.com, internationalcardio.com
mydestination identifies the domains this server accepts mail for. In this setup it will accept mail addressed to @mail.redcedarpoint.com (assuming you fix myhostname, as above), @localhost.redcedarpoint.com, @localhost, @dmcwatering.com and @internationalcardio.com
Nowhere here does @recedarpoint.com appear, so users won't get mail addressed to [email protected]
It's easiest to just add redcedarpoint.com to the list of domains the server handles mail for.
how should I setup DNS from my hosting service
Your subject implies a reverse DNS question, but there's nothing in this post about reverse DNS. Other than that, you should have an MX record for your domain that points to the public IP address of your router.