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Deliverability – improve it, or waste your marketing budget

One of the easiest ways to improve the RoI of your email marketing is to increase the proportion of your emails that get through. It’s not rocket science. But, says Paul Crabtree, it’s about more than just RoI. Fail to get to grips with data hygiene and you risk falling foul of increasingly sophisticated anti-spam systems, and the less forgiving attitude of ISPs.

By Paul Crabtree

The latest research shows 98% of all email traffic is now spam (Source: IronPort Systems 2008 Internet Security Trends Report). Of the 120 billion spam messages sent every day worldwide, 20 billion spam messages are targeted at the UK - a 100% increase on 2006. Microsoft alone is reported to block over 2.4 billion junk messages to its MSN and Hotmail subscribers every day (Source: BBC). With the tide of spam continually rising, regrettably 20–30% of legitimate marketing emails are accidentally trapped by filters (ie ‘false-positives’).

This poses a new challenge to UK publishers of ensuring their email marketing continue to be delivered and not caught in spam filters - in short, to keep deliverability rates as high as possible. So, while good design, segmentation and compelling content are important, failure to actually reach recipients means you are throwing away a proportion of your marketing budget and risking significant brand damage.

Investing in your deliverability generates extra revenue – improving from 95% to 98% means significant extra sales conversions. On the flip side, not investing means you run the risk of losing revenue when deliverability rates fall.

How? Deliverability is influenced by a number of factors:

1. Who’s sending?

Your emails are analysed by recipient email systems that evaluate their past dealings with you. Therefore, to improve things: suppress hard bounces from your email lists; include clear unsubscribe messages and respect unsubscribe requests; have a back-up relationship with an email service provider (ESP), this will help if you experience blacklisting problems; repeatedly encourage contacts to add you to their safe sender list.

2. What are you sending?

The copy and code of each email is analysed, including what links are used: if using a bulk sender ESP, use a dedicated sub-domain and check that activity by other clients will not affect your reputation; implement domain keys, sender ID and SPF records on your bulk mailing email server; always check your emails using a spam checking tool pre-send.

3. Can anyone vouch for you?

Being an accredited sender means you’re certified as reputable: invest time to build relationships with ISPs and antivirus corporate firewall companies to prove your reputation; alternatively work with an ESP to ensure your emails are whitelisted; consider schemes such as Goodmail or Sender Score Certified.

Managing bouncebacks

Reducing bouncebacks, and improving deliverability generally, is one of the most crucial email marketing issues. Businesses generally underestimate the importance of improving their deliverability. The latest E-consultancy survey of email marketers, the Email Marketing Census, February 2008, – the largest of its kind in the UK - shows 60% say deliverability is fine as is and don’t see it as a priority. Effectively, marketers can boost their marketing budget by, on average, up to 14% - this was the figure estimated as being lost through non-delivery.

Bouncebacks are not only wasting your marketing budget, triggering spam rules and potentially harming your relationship with the ISPs, but you are missing out on identifying replacements at recipients’ businesses. Repeatedly trying to deliver messages to addresses that do not exist triggers spam rules in web mail systems such as AOL - and the only answer is to suppress hard bounces from your email lists. Failure to have a management policy in place for bouncebacks is serious – it means over time, your delivery into inboxes progressively gets worse, the effectiveness of your email marketing drops as does RoI.

Hard or Soft?

ISPs sometimes penalise email senders if the messages they are sending result in a large number of ‘bounces’. Be sure to review your lists on a regular basis and remove from your lists any email addresses that hard bounce or that repeatedly soft bounce. We need to distinguish between these two: a hard bounce is an email message that has been bounced back to the sender undelivered because the recipient's address is invalid, or in other words - a permanent failure. A hard bounce might occur because the domain name doesn't exist or because the recipient is unknown.

A soft bounce is an email message that gets as far as the recipient's mail server, but is bounced back undelivered before it gets to the intended recipient, ie. a temporary failure. A soft bounce might occur because the recipient's inbox is full. A soft bounce message may be deliverable at another time or may be forwarded manually by the network administrator in charge of redirecting mail on the recipient's domain.

Reducing the number of hard bouncebacks will help aid deliverability and increase the chance of mail hitting the inbox for addresses which do exist. Properly configured email marketing systems will automatically handle bounceback processing for you, to ensure that the lists you are using to send messages are as clean as possible.

List cleansing

Regular list cleansing is essential for any emarketer as, perhaps obviously, it makes marketing activities much more effective and helps enable segmentation. Clearly sending repeated email messages to people who have gone is a waste of resources – this money could be spent on acquisition activity! However, the Email Marketing Census found only 57% of marketers performed regular list cleansing and a fifth of respondents said they hadn’t incorporated any list cleansing at all. In addition, the quality of email database was cited as one of the top barriers to effective use of email marketing. So, it seems that while we know it is necessary, a worryingly high proportion of marketers are not performing adequate database cleansing.

Bounceback trends

According to the DMA’s National Email Benchmarking Report (Q2 2007), hard bounce rates are down, suggesting that marketers can see the benefit of investing in data hygiene and may also be using confirmation emails to validate new email addresses collected. The report showed some ESPs were not removing an email address until they had received five hard bounces. As it is unlikely that the address or domain will become valid, and by not keeping their list clean, this may damage their reputation with their ISP, in turn affecting future delivery.

Average hard bounce rates are around 4% for acquisition emails and 2% for retention, however even a slight improvement can pay big dividends in the long term.

The DMA also found there are more messages being blocked as spam, and less bounces being caused by full mailboxes, as many providers increase their storage capacity. For the first time this quarter, "message too large" has been given as a reason for bounce. Limiting the size of an email could be one thing every email marketer can easily implement to ensure a better chance of delivery and thus being read in full.

Reasons for email bounce

* Spam traps. A spam trap is an email address that is created for the sole purpose of catching senders of unsolicited / illegitimate email. Any email messages sent to these addresses is, by definition, spam. And if you're caught doing so, you will immediately be put on the ISP's blacklist.

Spam traps are a common technique used by receivers, ISPs and filtering companies to identify senders with poor data collection practices. Maintaining an accurate subscriber database is a cornerstone of email best practices, and receivers have a low tolerance level for senders who mail to their spam trap addresses. Hotmail has recently started to recycle addresses that have been dormant for some time and use these as spam traps.

ISPs typically post spam trap email addresses on different websites waiting for them to be "scraped" or "harvested" by spammers or not-so-honest list brokers. Email marketers using new lists for acquisition purposes must be very careful when they don’t know how permission was obtained (eg. rented or bought lists, lists from marketing partners etc). The best way to avoid emailing abandoned Hotmail accounts is good list hygiene. Ensure you remove bounced addresses from your mailing lists, be careful when sending email campaigns to a list that you haven't used for more than six months and be extra careful when using third party email lists.

* Churn rate. Churn rate, as applied to a customer base, refers to the proportion of subscribers who leave a supplier during a given time period. The number of bouncebacks gives a good indication of churn rate – in other words, it gives a good idea of the life expectancy of the address. For example, in the academic sector, this is likely to be a long time, perhaps five years upwards, however for IT professionals it will only be 18 months.

Are you wasting budget on emailing dead addresses?

Just because an email bounced, don’t necessarily give up, there are other options. Through the use of other channels, such as direct mail, emarketers can use a technique which is common in B2B markets: communications are addressed to the job title, eg. ‘The Marketing Director’. This title slugging can re-activate contacts to whom email marketing activity can begin again.

Re-mailing hard bouncebacks may not always be a good idea (and could damage your reputation with ISPs). Following a typical campaign, one retry is worthwhile, however mailing hard bounces more than once is pointless.

Future trends

Recent trends have seen new ways that email is being handled – systems that treat everything as blackmail, such as Spamarrest, are growing in popularity. However, false-positives are caught in the filter which are not supposed to be there.


Effectively managing bouncebacks, employing list cleansing techniques and improving deliverability rates overall will significantly improve the effectiveness of your email marketing, make budgets stretch further and help your online reputation.