Because a salesperson I know could not send mail to my domain (rare-it.com), I checked the mailserver log to find out what was happening. Turned out that his domain did/does not have a proper reverse DNS-lookup. That is, the IP address of his mailserver resolves to another hostname than he sends his email from. This is true for my domain too, but I have my office at home, and have a normal connection with a regular ISP. His domain is from a company that exists for about 10 years now.
So, I decided to turn of the reverse DNS check for a moment. I know I switched it on to prevent spam, since most spam is easily filtered because of the failed reverse lookup.
Today I had 24 e-mails MORE spam than the regular 1 or 2. That’s 1 day. You know what will happen when I leave this backdoor open. Backdoor is closed again. Nailed shut. Big iron bar. And just to be sure, a bouncer as well. You never know.
Aug 032006