jmthompson wrote:
And it can be even worse; I forgot to mention that it's also common practice to blacklist incoming mail from IP blocks that are known to be assigned to residential cable and DSL customers.
Well, I don't have that problem. Both of my servers have proper PTR records, which means reverse lookups at the receiving end will show a fully-qualified domain name for either machine that is my domain, not the ISP’s. Otherwise, you are correct in that a mail source from a machine without a PTR record that points back to a FQDN other than the ISP's generic machine name will likely be blocked, at least on port 25. My servers, in fact, will refuse port 25 if a reverse lookup results in a FQDN that doesn't match the FQDN provided as part of the EHLO initiation sent by the foreign server. That alone will stop 90 percent of the junk flooding in through the gun ports.
As for system security, any Linux administrator will know how to take care of that. Unlike Windows, Linux's security is an integral part of the kernel, not a series of patches to fix problems as they are discovered. While my servers do undergo attack now and then, like most servers that are directly exposed to the Internet, I am careful about passwords, privileges, file permissions, etc. I've not had a successful breach to date.
I never said there would be a free lunch with this. Yes, some elbow grease is required to get it running and keep it maintained—and of course, you will need at least one static IP address for the mail server. Plus there is the necessity these days of having a valid SSL cert and following through with the mandatory annual update. That I've been doing it from a residential location for some 20 years should make it clear that it is more than possible.
Quote:
BTW I' not surprised you like sendmail. The config file looks like old school line noise. 
Periodically, I've entertained switching to Postfix. However, I've been working with Sendmail since the 1990s and for some strange reason, all that punctuation-like stuff in the sendmail.cf file seems to be intelligible. My sendmail.cf is heavily customized to work with my automated anti-spam stuff, which meant I had to learn how to work directly with the configuration without using the M4 macro processor (which I've never liked). So I bought the so-called “bat book” from O’Reilly and read and read and read until I figured I knew what was going on. That knowledge has been useful in working with clients' systems, as I have several who host their own mail in-house.
