An Email Server Admin’s Guide To Getting Your Mailing Lists Delivered

by Mike Chiasson on July 8, 2011 · 6 comments

Although email marketing has never been my thing, I would like to some day really crank things up in that arena. I was reading a thread over on the IM Grind Forums about ‘Avoiding SPAM Filters’ with your email lists. It got me thinking that the majority of people probably don’t get to see some of the back end stuff that sets up rules for SPAM on large enterprise lists. So today is your lucky day as you are about to learn some lessons and pickup a few pointers on how to get past spam filters.

Typically when you have someone who manages a spam filter you are talking about a corporation or large company. Often times personal users with their cloud services like yahoo, gmail, msn, etc. already have built in spam filters that are largely way more complex and better than the corporate users. They can do this with Bayesian filtering which lets your filter ‘learn’ spam trends. So when gmail receives 10,000 bizopp emails a second, they can learn pretty quickly which emails to flag.

So why exactly do corporations have various different spam filters? Well the main reason is that its a growing problem, and no one has the end all solution. Some companies¬† might use a Lotus Domino mail server with Lotus Notes clients while others use Microsoft Exchange with Microsoft Outlook clients. There are literally dozens of email server configs and just as many spam solutions. Personally I’ve worked with about 5 different spam protection providers in my IT career. Everything from cloud based filters to old linux desktops doing the filtering. I’ve even relied strictly on the email server’s capabilities itself.

Why Doesn’t The Email Server Just Block Spam?

Depending on the amount of spam you receive in, it can literally cripple your email server. I’ve had mail server crash on me and be qued up for days at a time just trying to reject all of the spam. Although this can still happen to a spam filter itself under certain loads, at least the mail server could still deliver external mail and allow internal mail without delay if something like that happened.

The Barracuda Spam Filter

So the current packages I have been working with are products of Barracuda networks. I really like these now because they are pretty much completely hands off. I have it synced to my active directory accounts so I don’t need any manual updates, and it always downloads daily updated from Barracuda itself. Definitely a pricier option but so convenience to be this easy.

Here is the main control panel

Barracuda Spam Filter Control Panel

As you can see since bringing this box online in January it has taken a beating. My server has received over 1.75 million emails, upon which only about 105k or so were authentic non spam based. Imagine sorting through that huh?

If you go into see the default Spam Checking area you can see the following setup. Please note 99% of the people configuring something like this would leave all the defaults here unless they experience a problem.

Barracuda Default Spam Score

The default ‘BLOCK’ command for the Spam Filter is ‘5’. So if your email rates over a ‘5’ it automatically gets deleted…too bad for you. The ‘Quarantine’ is disabled here only because these are global settings and by default the quarantine is set to user settings. The ‘Tag’ feature would append a name onto the title of the email so the user knows it may have spam. IE: If the email title is “Check out these girls yo” it might change it to “[SPAM?] Check out these girls yo”.

Needless to say your goal is to have a smaller score for better chance of delivery. Most commercial mail service providers, like Aweber, provide a way for you to have a good idea of the score. Aweber utilizes Spam Assassin which is a really popular measurement on a lot of linux boxes and will definitely be pretty close scoring across the board, but DON’T RELY ON IT! If it says ‘3.5 you are good to go’ that means redo your email because it will probably get picked up somewhere as spam.

AWeber Spam ScoreCan We Sneak In Images?

I see this all the time where people will just embed an image with tons of text in it. A lot of time spammers on Craigslist do this. Unfortunately those days are gone in email as well. Barracuda and most other providers will actually scan your images for text and flag you on spam for it. I don’t think Aweber does this though, so just because it might say you are safe, doesn’t necessary mean you actually are! By default this is enabled on most filters.

Barracuda Image Scan

Well I Can Still Have Good Text And Get My Affiliate Links In Right?!?

Yikes you really are a sucker aren’t you? Here are a couple things you need to understand. Not only can email domains get blacklisted but so can regular URL domains as well! For example in the last 2 days I received almost 6,000 emails that weren’t blocked as ‘spam content’ but were blocked because they contained a URL that was blacklisted. Let’s look at the example below. If interested you can download the full list here.

Blocked Spam URLsSo if you send an incredibly designed email with an affiliate link or redirect from ‘’ you just completely blocked. An easy way to see if you are blocked would be to go lookup your domains in various blacklists. I prefer to use Barracuda’s BRBL service just because they typically aggregate from Spam Haus, Spam Cop, etc. You can check your own domains out at Below you can see what happens when we query for

ZOMG Blacklisted

In the image below you can see a few of the emails that got blocked for having URL’s on the list. Its a shame because some of them are actually pretty well written.

Blocked Emails from Intent

Notice we have 'Voip' and 'Penny Auction' offers in this screenshot.

Hmmm Maybe I Can Just Use URL Shorteners?!?

I don’t blame you crazy email marketers for thinking like this, but this is an even bigger risk. Aweber had an awesome article released the other day about how using shorteners are bad. I recommend reading the full article at however I will copy and paste the real meaty chart they did up for us here.

Blacklisted URL Shorteners

I think the most itneresting things here are that is flagged on one blacklist and and are actually whitelisted by some! BTW being on a national spam provider’s whitelist is basically the ultimate for email marketing delivery. Goodluck getting on there though!

Ok After 1.5 Million Spam Messages You Must Know Everything Right?

One of the benefits of running a spam filter and email server is that you can view everything. Not that I do too much email marketing but if I ever wanted to build a list about credit reports…well I just query my filter for ‘Credit Reports’ I can see what sort of emails are coming in. This gives me an EXTREME advantage to be able to see what sort of emails people are sending out. See below a quick query and the results.

Credit Report Emails Incoming

Even better though. I can just query to see everything that got by, so I know what I could pretty much replicate!

Credit Reports Allowed

Damn This Post Is Long…Is It Over Yet?

Ok ok. Lets wrap this post up already. Bottom line, we all know that we can’t be too spammy but most MSPs don’t actually show you half the crap that might block your mails from reaching the list. Hopefully you learned a few tips from seeing the sort of crap I have to deal with and seeing how you can avoid being caught by the filter.

As usual I received no compensation for this post or any products mentioned herein, however I am an active user of both Aweber and Barracuda products. Note that they each sent me t-shirts. Holla!

AWeber and Barracuda T-Shirts on Mike Chiasson

About the author

Mike Chiasson Mike Chiasson is the Director of IT for a publicly traded company by day and an Internet Marketer by night. He absolutely hates the words 'serial entrepreneur' but loves discussions about business. You can follow him on Twitter.

DinoVedo July 8, 2011 at 3:45 pm

Awesome post! I actually read that thread too… I use aweber, but I still get into spam folder most of the time..

I tested using my tracker domain as the link, and then using a redirect on a niche website domain I have.. My tracker domain went to spam, and so did my website one.. but when i used a shortener, it went to the inbox..

And no my domains arent listed in the blacklist so i find it strange!

Mike Chiasson July 16, 2011 at 8:38 am

Yeah depending on what filter is being used it can be different for everyone. The one I linked to above is specifically Barracuda's. They do subscribe to the major blacklists but places like gmail, yahoo, etc. probably have their own massive setup.

onyx26 July 14, 2011 at 8:06 pm

awsome post . I wish with email spam they can do some sort of filtering as what askimet does for blog post.

Mike Chiasson July 16, 2011 at 8:38 am

Haha they do. That is identical to what a spam filter does man.

Joseph Bison July 14, 2011 at 9:19 pm

Great post , you never stop learning in this business

Mike Chiasson July 16, 2011 at 8:39 am


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