Dreaded SPAM

Spam. Ick. Here are a few notes on SPAM and Moxy.

Sending spam

Moxy doesn't want to send spam. Under normal circumstances, mail received for a domain not listed in the domain database will be rejected with a Relaying Denied message - so Moxy only accepts mail for domains it is explicitly configured to accept. If mail comes in for a domain that is in the domain database, a connection is made to the destination host and port, the MAIL FROM: and RCPT TO: are transmitted to the destination which determines if it will accept the mail and its answer is returned to the sender.

There are two exceptions to this. The first is when allowRelayFrom and sendRelayTo are configured to allow relaying from a specific range of IP addresses (see the configuration page). In this case all mail from the IPs listed in allowRelayFrom is accepted and sent to sendRelayTo - so be careful you have only trusted IPs listed here.

The second exception is when using the nodb database type (see the config page). This "DB" type is mainly used when all you are interested in is logging mail bandwidth. The problem here is that mail for any domain is accepted and proxied to the hosts listed in the nodb_dest configuration parameter. Those destinations must be configured to accept mail from the Moxy host but, if you don't want to look like an open relay, they need to be setup such that they won't simply transmit mail for just any arbitrary domain. How this is done is dependant on the MTA used and is up to you.

Receiving spam

Moxy proxies mail connections between senders and recipients. At this time, it does not attempt to reduce or eliminate spam but leaves this up to the recipient's mail server. The only disadvantage of using Moxy is that - since all incomming mail connections arrive at the Moxy host and are forwarded to the recipients' host - from the recipient's point of view all connection originate from the Moxy host. To allow users to track down the actual sender, Moxy will prepend a header to each mail message of the form:

Received: from [206.10.25.251] 
        by moxyhost.com (Moxy Mail Proxy); Mon, 03 Dec 2001 14:35:39 -0800

if the appendRcvd parameter is set in the config file. Other data exchanged during the connection (such as the MAIL FROM: and RCPT TO:) are unchanged.

If you feel it would be usefull to incorporate spam filters into Moxy or if there is a specific program you think Moxy should be able to interoperate with, please let me know.