On Friday 29 February 2008, Brent L. Bates wrote:

 We've been using milter-greylist:

http://hcpnet.free.fr/milter-greylist/ ftp://ftp.espci.fr/pub/milter-greylist/

for almost a year now and it works great. I looked over a number of other options and I believe this was the only one that was a compiled executable. I think all the other ones I found were scripts and I wanted something faster.

My $0.02.

We've been using milter-greylist on CentOS4 for several years. It works well, but has the following issues:

1) On lightly loaded mail servers, it reduces load by cutting overall mail volume. On very busy mail servers, it can be a performance hog. I guess its internal database search algo could use some beefing up. In our case, hosting around 10,000 email accounts for about 500 domain names, we have two otherwise cheap machines with lots of RAM dedicated simply to greylisting incoming email. EG: ATA is fine, very little disk volume.

2) Very stable. (maybe 3x in the past 4 years, milter-greylist gets out of synch with its own socket file and it has to be re-created)

3) It is fabulously effective against "spam attacks". We would see spam coming in periodic runs, from a large number of addresses around the world, in a burst that might last perhaps 4 hours. During these attacks, we'd see a very large volume of spam being delivered to random to addresses within our domains. A typical spam attack was probably around 250,000 messages, and would bog down our servers for a day or more dealing with all the virus filtering, spam assassin scanning, failed delivery notifications, and undeliverable failed delivery notification messages, while the load shot thru the roof. Greylisting stopped this COLD, and this is why I first started using it.

4) It installs effortlessly with sendmail. I've never tried to install it with other MTAs.

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