Here are the instructions on how to set up our anti-spam service for customers who maintain their DNS by hand.

If you use Plesk to manage your domains, there is a step-by-step setup guide which you should consult instead.

Before you start

This is a cheap, but chargeable service! See the product description page for prices.
It is currently only supported for mail servers within Bytemark’s network. Do not try to set up the service for mail servers outside, your mail will get bounced.
For the service to be completely effective, you will need to lock your server down which may have some side-effects on clients using your machine to relay mail. See our lock-down page for more details.

Two minute setup

We will use the domain example.com to show how to set up mail filtering, and assume you are using our content DNS service

Currently you will probably have one or two MX records pointing to your existing mail server. Here is what your configuration might look like:

@example.com:1.2.3.4:a:5
@example.com:1.2.3.5:b:10

i.e. you have two MX records, one at a.mx.example.com with IP address 1.2.3.4 and a distance of 5 (your primary), and b.mx.example.com with IP address 1.2.3.5 and a distance of 10.

You need to do two things: one is to hide the address of your real mail servers from spammers, and the other is to publish our mail servers as the exclusive destination for your mail.

# Tag my real records so only Bytemark can see them
@example.com:1.2.3.4:a:5:::nospam
@example.com:1.2.3.5:b:10:::nospam

# Tell the rest of the world to go via Bytemark
@example.com::a.nospam.bytemark.co.uk:5:::world
@example.com::b.nospam.bytemark.co.uk:10:::world

And that’s it! Upload these records and watch the spam disappear.

Please note you shouldn’t need to use any “backup MX” service including Bytemark’s. Any other MX that accepts email for your domain directly is going to be found and exploited by spammers – make sure our servers only deliver direct to yours, and that no other server is allowed to accept email for your domains.

What happens next?

Because of the way that DNS works, it will take a few days before email starts flowing through Bytemark servers exclusively, but you should notice an effect after the first 24 hours.

Each Bytemark account is allowed a 30-day or 1GB trial period – you will receive an email when you configure your first domain to confirm that charges may be pending, and when the trial is over, to confirm that charges will be added to your account.

Locking your server down

Once you’re happy with Bytemark’s anti-spam service and are using it on all your domains, you should consider locking down your mail server to only accept email from our anti-spam servers for maximum effectiveness. See our lockdown page for more details.

Advanced tuning

Here is the full list of parameters you can set up for each domain. All advanced parameters are published as TXT records within the .nospam.example.com domain. Our examples show these records as being published globally since there is no real security risk to them, but you can also add :nospam to the end of each line to hide them.

Setting your own bounce message

You can set the message that senders receive when their message is rejected by setting the ‘bounce’ parameter to be any message up to 255 characters long:

'bounce_message.nospam.example.com:Your\040message\040has\040been\040rejected\040by\040example.com's\040anti-spam\040system.\040\040Please\040call\040084500000000\040if\040this\040is\040unexpected.

You should use a TXT record builder to make sure your escape all the necessary characters properly.

Turning off greylisting

Greylisting is a highly effective anti-spam measure which enforces a brief delay to email sent by anyone that hasn’t sent mail to your domain within the last 60 days.

If this delay is a problem for a particular domain, you can disable it by setting the ‘greylist’ parameter to ‘f’ (false):

'greylist.nospam.example.com:f

Turning off greylisting will make the spam filtering noticeably less effective, but will make sure you receive every email as soon as it is sent.

Turning off virus filtering

If you don’t want to use our virus-checking (if you pay for a separate anti-virus service for instance) you can speed your mail up a little by turning it off:

'antivirus.nospam.example.com:f

Turning off anti-spam altogether

If you only want to use our service as a virus filter, you can do so by turning off anti-spam content scanning altogether:

'antispam.nospam.example.com:f

Quarantine facility

If you wish to test out the filter without risking it rejecting email, you can set a quarantine address which is where any email suspected of spam will be sent instead of being rejected.

'quarantine_address.nospam.example.com:quarantine@example.com

This will send any suspected spam or viruses to quarantine@example.com.

Altering your spam scoring threshold

Our content scanning assigns a score to any incoming email and will reject as spam any email that exceeds that score. By default it will reject messages with a score of 6. You can change this to whatever you like:

'spamscore.example.com:3

If you lower it you will probably catch more spam but also may turn away some legitimate email. We do not recommend altering this without also using the quarantine facility to check your results for a couple of weeks.

Topics:

Mail Spam Tutorial