Troubleshooting outbound email issues

If you want to be "one of the good guys" and follow the rules by which spam is sorted out from other mail servers, you should follow some of these guidelines:

(Note that some basic knowledge isn't covered here; You should know what an MX record is, for example.)

Sending email directly from residential (home Internet) addresses is not likely to work well. Most ISPs block port 25 on residential services, and even if yours doesn't, there will be RBLs blocking you from the start. If you must run a server from a residential network, you will probably need to add a third-party service to relay SMTP in and out.
It is possible to use a mass-market email service such as Yahoo or Gmail as your outbound SMTP smart host, but all email will be stamped with the address of the provider account instead of the address of the original sender.
If you are on a static IP address on the Internet, you should make sure your DNS and Citadel Settings match the following criteria:
You should configure your Citadel server's Fully Qualified Domain Name to the correct value; for example, mail.yourdomain.com. This setting can be found in WebCit under the Administration menu.
Find out the IP address from which your outbound connections originate. From your Citadel server, you can use a command such as
```
curl ifconfig.me
```
to retrieve your public IP address - for example, 123.45.67.89
Make sure this IP is resolvable via Reverse DNS to the correct name (such as mail.yourdomain.com). The command will be something like
```
host 123.45.67.89
```
Reverse DNS is usually configured by your ISP.
Make sure that your host is one of the listed MX records for your domain. For example, mail.yourdomain.com should be listed if you run a command such as
```
host -t mx mail.yourdomain.com
```
Of course, you should also make sure your forward DNS lookup works properly, with a command such as
```
host mail.yourdomain.com
```
resolving to the correct IP address (such as in the above example, 123.45.67.89).