Email Filtering

iRedMail comes with self-updating blacklists and SpamAsassin for sorting out spam. Email delivered from a server listed on a spam blacklist (e.g., lists from Spamhaus) are rejected; other email that looks suspicious will be classified as spam, as well. ClamAV is also included to identify messages carrying malware and isolate them.

Although the implementation delivered by the downloadable installer is serviceable, it is a bit disappointing. In the default configuration, spam is sent to quarantine instead of into the recipient's Junk folder, which is the behavior most users expect. Additionally, SpamAsassin does not perform Bayesian filtering and does not autolearn. Ideally, an email server should be able to learn which email users want to read and which they don't to adapt the filters to their preferences. In a typical email server, this is done by having the spam filter take notice of which email is manually moved into the Junk folder by the users, and which email accidentally placed in the Junk folder is moved elsewhere by the users.

The iRedMail instance you get from the downloadable installer can be configured to behave properly with autolearning spam filters that place spam mail in the Junk folder, but it is a somewhat involved process [8]. iRedMail Easy does the correct thing out of the box and does not force you to tweak spam filtering manually. There is no reason at all why the downloadable installer couldn't do the same. My hunch is that iRedMail Easy takes the proper approach and the downloadable installer takes the crude approach because the iRedMail organization wants to push you into using iRedMail Easy.

Conclusion

If you need to deploy an email service for a small organization (e.g., you need an email provider for a single domain), the iRedMail downloadable installer is an option worth considering. It will certainly turn a machine into an email server very fast, with most of the features you expect included.

One of iRedMail's strengths is its portability. Other free open source software email appliances (e.g., Mail-in-a-Box) work on a specific distribution or operating system, but iRedMail can run on an astonishing number of platforms. Because of this advantage, if your server fleet comprises instances of a given system (e.g., OpenBSD), the system administrator won't have to set up an alien platform just for email.

On the other hand, if the out-of-the-box configuration does not work for you, you will have to perform a number of manual steps that negate, up to a point, the advantage of deploying an easy-to-roll solution. Specifically, if you need to change the default configuration of the spam filter, you will have to face a quite involved process. Also, adding more domains to your mail host is doable from the iRedMail's control panel, but adding DKIM keys for those domains (which is a necessity these days) must be done manually from a console. In any case, iRedMail still takes less effort than building a full email stack manually from the ground up.

The Author

Rubén Llorente is a mechanical engineer who ensures that the security measures of the IT infrastructure of a small clinic are both legally compliant and safe. He is also an OpenBSD enthusiast and a weapons collector.