Dec 08 | 4 minutes read

To reach the inbox

Is it really necessary to care about deliverability in connection with email marketing?

Oh yes.

In the fall of 2005 a study was made among American companies using email marketing. More than 60 % answered that problems with deliverability was the biggest one of all. About the same time another study was made in the US, which stated that more than 20 % of all legitimate email messages disappeared on the way to the recipients due to various spam filters. Studies that we conducted ourselves in Sweden show that the corresponding figure here is about 15 %.


The question about how many of the mailers’ messages that are classified as spam gets different answers depending on who you ask. Figures between 80 – 90 % are not uncommon.

From the beginning a spam filter searched for words and phrases like “Viagra”, “Get rich quick!” or “Congratulations! You’ve won the lottery!” If an email contained any of these words or phrases it was probably a spam and the message was deleted.

The senders of spam didn’t like that, of course. One way to avoid this type of checks was to change the words so that “Viagra” was “V1agra” for instance, “get rich quick” was changed to “g3t r1ch quikk” etc. So in order to keep up with the changes the developer of spam filters needed to search for words similar to the typical spam words as well. This naturally reduced the precision and increased the risk of mistakes. (There is a rumour that the Swedish community Villaägarna for instance had some problems with too zealous email filters.)

The solution for those who was sending spam then was to “hide” certain words and texts in images which is much more difficult for a filter to analyse. The answer from the developer of spam filters was to search for email messages containing a suspected amount of pictures.

A problem with all these methods is that they cannot take the absolutely most important aspect of spam in email marketing into consideration: the ethics of the sender.

It might not be very usual, but absolutely legitimate emails may of course contain the word “Viagra” (ask a pharmaceutical company) or a large share of images. Therefore you can very well say that if email filtering is based on the reputaion of the sender, then it is okay – even if it fails sometimes, as do the other techniques. This type of filtering is based on the fact that recipients who are dissatisfied with email messages they received from a certain mailer do report this and that the email servers that have been sending a lot of these reported messages become blacklisted. The receiving email servers are then able to refuse email messages from those blacklisted servers. 

Apart from the above mentioned methods technical obstacles are relatively common phenomena that might stop unwanted email messages. Typically this means that the one who operates a receiving email server:

• adds a short delay before received email messages are forwarded to the recipients. If too many messages have been sent from a certain mailer during a specific period of time this might be interpreted as spam.

• makes the server send a failure message at the first attempt to reach the receiving email server containing a request to try a little later. This technique is called “greylisting” and it means that certain types of virus cannot interpret the failure message and thus won’t try again.

• intentionally makes the receiving server slow when it comes to answering the server that sends email messages. The idea behind this is that several sending servers are short of time and will not wait as long as it takes.

• keeps an eye on whether there are many bad email addresses to the receiving domain in question. Lists that are not properly taken care of are seen as an increased risk for spam messages.

What can you do as a sender?

Pretty much, in fact.

1. Make sure that you have access to the most common filters on the market, filters that analyses the contents of the messages. Check the messages before you send them. This means that you also should have an address on Hotmail and Gmail and make a test there.

2. Don’t “modify” your code of ethics. Stick to it!

3. Make sure that you use an email technique which doesn’t fail because of “greylisiting” and which checks recipients for messages about “too many sent messages”.

4. Delete bad email addresses from your list.

5. Use the authentications technologies like Sender IP, DomainKeys and Sender Score Certified. These are techniques that help the recipients to feel sure of the fact that the email messages that you send aren’t from faked sender addresses and that you follow certain ethical guide-lines. All this improve the possibilities to get through.

6. Avoid some of the technical pitfalls like IP numbers in links (they are interpreted as false links by newer versions of Outlook), tracking of written links (the same thing) or to send newsletters that consist of one or several images only.