How to ... avoid e-mail bounce backs

There are several reasons for a returned e-mail, but often the most frustrating is when a firewall makes the decision. But there are ways to avoid the spam traps, says Gavin Wheeler.

E-mails that bounce back are the bane of direct marketers' lives. The necessity for and proliferation of firewalls has made e-mail bounce back an unavoidable sign of our virus-ridden times. Yet there are some fundamental things that can be done to avoid the dreaded 'undelivered' message popping up in the inbox.

Escape the spam trap

Spam traps are a necessary evil for the industry. But it is possible to minimise the likelihood of the spam filter kicking in by watching the words used. For instance 'unsubscribe' and 'fantastic savings' will trigger a spam filter. As will certain patterns and certain designs. A good guide to what a spam filter may reject can be found at

Scaling the firewalls

Corporate firewalls are renowned for bouncing back e-mails. As a large proportion of consumers receive and respond to their personal/private e-mails while sitting at their work desks, this should sound some alarm bells. Check the file size as well as the content. Files greater than 50K, complex flash or hi-tech sequences typically risk bouncing back. And HTML messages often fall foul of firewalls. They look good which is why clients often prefer them. So, if that's their preferred format we always send an embedded text version to which the ISP or corporate firewall can default if it rejects the HTML style.

Address check

Incorrect e-mail addresses and full in-boxes are common culprits for e-mails being returned to sender. The problem is that running tests to check e-mail addresses is an imprecise science and not wholly useful.

Time can be better spent monitoring the bounce-backs from unrecognised addresses. The 'three bounces and you're out' philosophy is a good rule of thumb. It allows for a full in-box or other online fault being the initial problem. But, after three consecutive bounces, it's pretty safe to say the address is incorrect.

Go another way

If another company spams your target address before you attempt to send a legitimate message, they can ruin the path for you. Spam filters can block incoming mail for up to three days. So if your message follows spam from the same IP address, it will be stopped. This risk can be minimised by using a number of IP addresses from which to send e-mails.

Pre-flight checks

A last 'pre-flight' check will pick up broken links, images not loading correctly and subject line, character encoding or mail-merge problems.

We also test on a number of different e-mail clients to make sure they can all receive and interpret the incoming message.

It's not a good idea to lose the e-mail style and format in translation just for the sake of checking and tweaking to suit the main ISPs. Once they're all accounted for, we know that the vast majority of recipients will receive our clients' messages as loud and as clear as we sent them.

- Gavin Wheeler is managing director for WDMP


E-mail was chosen to directly communicate the launch of a new free calls offer from TalkTalk, The Carphone Warehouse's fixed line brand. This offer was already high-profile thanks to national advertising and the fifth Big Brother's sponsorship on Channel 4. The e-mail therefore had to be similarly confident.

The Carphone Warehouse called in its direct response agency WDMP to achieve a tough acquisition target.

Existing Carphone Warehouse mobile phone customers and cold prospects were the targets. WDMP used a few cold list sources, including IPT and The Mutual, to be confident of a decent list, as well as its own database.

WDMP worked systematically with the e-mail distributor to minimise bounce-backs. This included careful use of subject lines and body copy to sidestep spam traps by avoiding sales phrases such as 'unbeatable offer' and 'huge savings' that are typically stopped by spam filters. The graphics were colourful, but their size - at less than 50K - fell well within the capabilities of domestic PCs and corporate firewalls. The e-mail was rigorously tested, sent to several e-mail accounts at a number of different ISPs and then finally sent from a fresh IP address.

There were some bounce-backs but only about ten per cent (compared to the 30 per cent typically experienced). WDMP re-mailed the bounce-backs and applied its 'three strikes and you're out' philosophy.

The e-mail campaign saw a huge reduction in bounce-backs compared to previous campaigns. And an impressive 40 per cent opened the e-mail and more than 19 per cent clicked through.

This and the offer ensured the tough target set was met comfortably.


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