2021 – Jean's Blog

Amavis’ cool features

I guess that most people use amavisd-new together with spamassassin and for example ClamAV. Probably a few more use features like DKIM verification and signing with amavis. However, there are some features which aren’t found in the usual howtos. Here are some of them.

systemd multi-instance Redis

Instead of working with one redis server instance I would like to use multiple instances of redis because that way I can limit memory and do additional tuning for the instances. systemd can help on this. I will create an instance for amavisd-new in this guide.

How I configure my sites in NGINX

Tuning / Improving your security using external online tools would be another possible headline for this article. There are a few pages I regularly use to optimize my configuration. Here’s a small guide.

Setting up amavisd-new and amavisd-milter

Amavis is not a new tool, in fact AMaViS started as a shell program back in 1997. Imagine, at that time I was 12 and kept annoying people on IRC. Anyway. In this article I’ll show you how to set it up, with a milter and policy banks. I also tell you about after- and before-queue filtering with Postfix and show you how to use both.

Amavisd-new and DKIM

Currently I’m playing around with amavisd-new and amavis-milter. Trying to analyse a maybe-bug I temporarily disabled DKIM signing. Then I had the glory idea to send an E-Mail to the amavis maillinglist. It sort of caused some mail reporting storm back to me. In this article I’ll show you, how you can configure amavisd-new to do DKIM verification and DKIM signing. But first, here’s one of those reports:

Setup MTA-STS and TLSRPT

What is MTA-STS (MTA Strict Transport Security) about?

MTA-STS basically enforces TLS for your mail communication, similar to HTTP Strict Transport Security (HSTS) for HTTP/HTTPS traffic. By telling the sender that TLS has to be used one can reduce / stop Man-in-the-Middle (MITM) attacks. A probably better explanation is found in the abstract of the RFC: