Open RatesIn the previous entries of this series we\’ve discussed why it\’s not simply enough to use open rates as the de-facto measure of an email campaign\’s success/failure. We also showed you how on a macro level to help your open rates via systematic processes. In the final part, we will talk about the content of the message itself and how that too can affect your email campaign results.

Content Filtering

In the past, content filtering was the primary method ISPs used to block bulk campaigns from getting through. If the content set off certain spammy words like indecent language, too many words like \”free offer\” and other suspicious sounding language, it would be caught by the spam filters and the message would be blocked. However, as spam grew to the epidemic now facing ISPs today, it became too limited to just go on content blocking alone.

Also, spammers got smart and stated to use images instead of text as the body content, rendering the filters useless for such messages. Still, many corporate spam filters do still have some level of content blocking so it\’s always a good idea to run your campaign through a spam checker to see if your campaign contains any of the verboten words.

URL Blocking

A step above content filtering are URL blocking technologies. Some ISPs do still use this as one way of determining if a message will get through or not. The basic idea is that the message content is checking against a blacklist of URLs that have been associated with spammers. The thinking behind it is that if your content contains one of the blacklisted URLs, then it means that you are probably a spammer as well. This, of course, might not necessarily be the case but the damage will already have been done by merely being associated with the blocked URLs.

If you are using an ESP, they will normally tell you the URL block and ask you to remove it. If you are doing this yourself, you will need to check the raw bounce logs to look for a specific notice about a URL block happening. This, by the way, is yet another reason why we really don\’t recommend you try to do mailings yourself.

Message Size

With so much spam clogging providers\’ networks, it\’s no surprise that some restrict the total size of the message to help minimize the damage. This means keep those pretty 1Meg high pixel rate photos off your campaigns if you want them to get through. A good general rule of thumb is to keep the total size of your message (including any images) to around 250K or less. While you may think that this might reduce the overall impact of your campaign by having not as high quality images, if the message gets blocked by the provider, it doesn\’t really matter how slick it looked since no one actually saw it.

Bad HTML Coding

The final content-related issue that can occur is bad HTML coding. By this I mean not only poor or incomplete HTML, such as not having the correct opening/closing tags) but also getting too fancy with the coding too. Hotmail, for example, won\’t deliver a message at all if it doesn\’t have the opening/closing tags, and many other ISPs will strip out advanced HTML like Cascade Style Sheets (CSS), rendering the message incorrectly. It\’s usually a good rule of thumb to keep the campaigns fairly simple to avoid such issues. Failure to do so can reduce the effectiveness of your campaigns.


As we\’ve explored in this 3 part series, the success or failure of your email campaigns goes way beyond simply calculating the open rates. There are more important metrics to consider as well as ensuring that your message gets through in the first place, from delivery issues to the content of the messages themselves. The days of fire and forget are over. To be a successful email marketer these days takes time and effort but those who do it the right way will be rewarded with superior results that go way beyond recording a bunch of opened emails.

Until next time.

Steve Chipman