In the last few months this topic has been the main talking point in the industry. Much of this talk is scare-mongering from suppliers who naturally have a solution to this problem. Talk of 80% of permission based marketing emails being blocked is completely un-true in our experience.

This article gives a complete overview of the deliverability issue and how you can reduce the chances of your email disappearing into the junk mail folder.

Types of filters

There are three main types of filter.

1. IP Address filters

The IP address of the server that sends your email is used by an ISP to identify the legitimacy of a sender. If the server has been deemed to have sent high volumes of Spam then your IP address may become blacklisted and therefore your email will not be delivered to anyone using the ISP or anti-spam service. The main blacklist, Spamcop.net will generally block a server for no more than 24-48 hours and can be triggered by a single report. However at ISP level (AOL etc.) blacklists are generated after a high number of Spam complaints – just a few people reporting you with the ‘Report as Spam’ button will not get you blacklisted. These blacklists are usually permanent and only human intervention at the ISP will remove an IP address from a black list.

These blacklists have become less useful to ISP’s as Spammers can simply keep changing their IP address to stay off blacklists. Therefore there has been a shift towards ‘White lists’ of IP addresses. This is where an ISP categorises an IP address as a legitimate sender of permission email. If an IP address is on a white list it may also bypass any content filters.

2. Content Filters (Server Level)

ISP’s use content filters such as Spam Assassin to read the content of the email. Each word that is considered to be used by Spammers is given a score. Each of these words scores is then added up to give a total for the email. If this total is above a certain user-defined threshold then the email will either be bounced or delivered to a quarantine or ‘junk mail’ folder.

3. Content Filters (Email client level)

Similar filters are also used by people as an add-in to their email client. Even a basic filter is included in Microsoft Outlook. This will much the same as the server based clients although they will always deliver your email but to a Junk Mail folder.

Content Tips

To help you write content filter friendly content think about the following:

Free, Offers, 100% guarantee
Avoid these sort of sales words – the filters.txt file on your PC which is used by Outlook to determine Spam emails will give you a good overview of what to avoid.

Unsubscribe text
Words and phrases such as “If you no longer”, “Unsubscribe”, “Remove” or “Privacy Policy” are all likely to gain a Spam score. Instead “Opt-out” or “Stop sending me emails” are better ways of phrasing this area of your email.

Subject line
Words in the subject line that are given a score will always be given a higher score than the corresponding words in the message body. Therefore place a priority on writing the subject line text to avoid Spammy phrases.

Click Here
“Click here” is the most used call-to-action in emails – however this is given a Spam score. Often you will have several “click here” links which will multiply the Spam score of your email.

Additional Tips

Testing – Don’t rely on content checking software

Content checking software will only give you a limited insight into the spammyness of your newsletter. Most are based on Spam Assassin rules that are freely available on the Internet. However major ISP’s such as Hotmail do not use Spam Assassin as Spammers can easily re-design their emails to get delivery. The only way to ensure your emails will get through to the major web-based email providers is to send tests to Hotmail, AOL and Yahoo accounts prior to sending the entire campaign. You can then change the content until the email goes straight into the inbox.

It is also worth reminding that web-based providers such as Hotmail alter their Spam filter settings according to the amount of emails that they are processing. Before Christmas many consumer marketers may have noticed a drop off in open rates and click-thru rates if they did not check the campaigns before delivering them.

Remove bounces

Many ISP’s including AOL score your IP address according to how clean your list is. If you continually send to out-of-date addresses then the ISP may take action and blacklist you.

Promote “Add to address book”

If your email address is in your recipients address book or safe list then your email will generally not be affected by content filters and be added directly to the inbox. This also means you should standardise on the From name and address you use.

White list your IP address

Your service provider should be white listed with all the major ISP’s. Hotmail is an additional cost as they use the Bonded Sender programme from Ironport. This requires you to post a bond that gets deducted by $20 every time a Spam complaint is received.