This article explains how our advanced spam filter works. The filter is included in our POP/IMAP email hosting packages. It is not included in our web hosting packages but you can purchase the spam filter as an addon.

How the spam filter works

A spam filter is a service designed to block spam. All our servers have a basic level of spam protection, which works for most people. However, if you are targeted by lots of spammers then you may need a more advanced solution. This is what our spam filter provides.

The spam filter does a large number of checks to determine how likely it is that an email is spam. Emails that are marked as spam are quarantined (held back) and you will receive regular reports on emails that have been blocked. You can also blacklist or whitelist certain senders and change the level of spam filtering.

Quarantine reports

When one or more or emails are marked as spam you will receive a daily quarantine report via email. The report lists the emails that have been blocked, and for each email you have the following options:

  • Deliver the email to your inbox.
  • Whitelist the sender. This will deliver the email to your inbox and prevent that future emails from the sender are blocked.
  • Delete the email.

You don’t have to actively delete emails that have been quarantined: emails that have been blocked are automatically deleted after five days. The report is mostly useful to quickly check if any genuine emails have been blocked.

Accessing the spam filter

You can also log in to the spam filter at st2.mx.email-filter.net. To log in you can use any email address you have set up. The password is always the password for the email account.

When you log in you see the Quarantine tab, which looks much like the spam quarantine reports you receive via email.

The spam filter's 'Quarantine' tab, which lists email that have been marked as spam.
Emails that have been marked as spam, sorted by their score.

You can again release (deliver), whitelist or delete individual emails. If you want more information about an email then you can also click on the listing. You can then view the actual email, as well as the email headers.

Spam filter settings

The spam filter has two other tabs:

  • The Settings tab lets you change how often you want to receive quarantine reports. You can also choose if the reports should show all emails that have been quarantined or just the emails that have been caught since the last report.
  • You can use the Filter Rules tab to blacklist or whitelist an email address or domain. For instance, if you want to block all emails from marketing@example.com then you can add the email address to the Blacklisted Email Addresses section. If you want block emails from any @example.com email address then you can instead add the domain example.com to the Blacklisted Domains.

Changing the level of spam filtering

The quarantine reports show a “score” for each email. This number is the “spam score” and it is used to decide if an email should be held back. The higher the number, the more “spammy” the email is.

By default, an email is marked as spam if the score is equal to or greater than five. If you find that some spam is filtering through the net then we can change the threshold. Please contact us if you would like us to make any adjustments.

One thing to note is that the filter will become more intelligent over time. It is usually best to give it a week or so before making any changes.

Routing emails to the filter

Each domain name has a number of DNS records that define how website and email traffic is routed. MX records define where mail for a domain should be delivered to.

To direct incoming emails for your domain to the spam filter the MX records for your domain need to point to the filter. There are two MX records for the filter:

  • st2.mx.email-filter.net.
  • st3.mx.email-filter.net.

MX records always have a “priority”. Both MX records should have a priority of 10.

If the DNS for your domain is managed by us then we will change the MX records for you when we set up the filter. We can’t change the records if the DNS is managed elsewhere but we are happy to talk you through the process. Please contact us if you need any help with the MX records.

Buying the spam filter

The spam filter is included in all our POP/IMAP email hosting packages. If you have a web hosting package then you can purchase the spam filter as an addon. You can do so via your billing account or by submitting a ticket. The price of the filter is £25 per year plus VAT, and the filter can be used for up to ten email accounts.