What do you do if you have a large volume of your customer database which has no email address alongside it, or has an email address that is no longer valid?

You obviously want to find up to date email addresses for these customers and the most popular (cheap) way of doing this, is to use an email append service.

This seemingly innocent process has taken a bit of flack recently, first being soundly thrashed by the Messaging Anti Abuse Working Group (MAAWG for short) and then very publically pilloried by Experian Cheetahmail.

So what has caused this to happen? And what should you consider before embarking on an email append project?

How does it work?

Email appending is the process of using a third party email list and implementing some sort of matching criteria (present on both your own and the third party data list) to link an email address to a person on your database. It is a process that can be fraught with issues, the first of which is the matching criteria.

You really need to make sure you match as much criteria as possible to ensure the person you are matching against is who you think it is.

For example, if all you have is J. Bloggs living at a certain address, but at that is address is a Joe Bloggs and Jane Bloggs, how do you know which one is your subscriber? The more information you have the better (age, gender), so you can be sure you are adding the right users to your list.

The next step is ensuring the emails you end up with have the correct permission to allow you to email them. The ICO (Information Commissionaires Office) recommends permission to use data that has been gathered for third party use, should have active “opt in” consent, not “opt out” implied consent.

In fact, the ICO also states in its advice to marketers:

One of the most frequent comments made in complaints we receive is… Where did they get my email address or mobile number from? I certainly didn’t give it to them.

2011 regulations by the EC Directive suggest:

You may wish to send a ‘low-key’ message explaining where you have got their details from and double checking whether they are, in fact, happy to hear from you in this way. You could not assume consent from their failure to respond.

The data quality issue

It’s this “failure to respond” that puts the biggest strain of the credibility of the process. Regardless of the legalities, using an “opt out” introductory email will inevitably lead to you having people on your database that don’t want to be there.

If you consider the numbers, in any campaign you are only likely to get a 20% open rate at best. Even if you do this three times, you are only likely to have been exposed to 30% of the match file.

This means that under an opt out regime 70% of your match list will not have signed up to be on your list.

This is bad news for two key reasons:

  • It can damage your brand credibility.
  • It can negatively affect your list deliverability and inbox placement due to complaints.

In fact, some email service providers refuse to accept appended email addresses due to the issues they cause. I know this all sounds negative, but let’s face it, there’s really nothing wrong with appending an email address to your client list, as long as the recipient wants to be there and has indicated as much.

And as an email marketer, you wouldn’t choose to damage your brands reputation, nor would you sacrifice inbox placement on purpose. So you need to consider carefully what the objective of the exercise is. 

Is it worth it?

If you are looking to enrich your database with valuable active subscribers that read your emails, the only way to accomplish this would be to encourage them to opt in. It’s going to be more expensive than taking everyone who doesn’t opt out, but the data will also be more valuable.

And this brings us to what the whole point of the exercise is, how much is it really worth spending to get this email address?

If, by appending this email address, you will obtain more business from the customer, how much business are we looking at? Alternatively, if the object is to save money over more expensive media, how much are you looking to save?

Once you have the answers to these questions, you know how much you have to spend on acquiring a responsive and recent email address.

It might justify a web based competition, or direct mail campaigns, or even a customer services phone call for your really valuable customers. Whichever way you choose to go, a live, responsive, email address is the only one worth obtaining.  

Tim Roe

Published 3 May, 2012 by Tim Roe

Tim Roe is Compliance and Deliverability Director at Redeye International and a contributor to Econsultancy. Follow him on Twitter, Google+ or connect via LinkedIn

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Comments (8)

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Peter Bell

Peter Bell, Managing Director at Fuse Lead Marketing

Great points Tim. The downsides of e-append are numerous and what looks simple on paper does not stack up when results and brand damage are considered.

Shameless plug here - there is an intelligent way to gain customer email addresses at low relative cost with high open rates, zero brand damage or conflicts with ICO guidelines.

over 6 years ago


Jed Mooney

I whole heartedly agree with most of the comments, particularly those regarding quality of data sources and accuracy of matching however, the "Is it worth it" seems to be based on concepts rather than facts, essentially its wrong!

The only reason I can say its wrong is because we run the largest single source of postal/email addresses, for email append, in the UK (e-Pool)and most of our recent orders are repeat. Where a client took some data a few months ago wanting to see, rightly so, if the email addresses proved to be responsive, and have since come back asking for more customer postal data to be appended.

Given many of our clients have their own insight teams who closely monitor response, CPA, CPR etc.... seems highly unlikely they are all wasting their money!

over 6 years ago

Tim Roe

Tim Roe, Deliverability and Compliance Director at RedEyeEnterprise

Thanks for your comments, I’m sure there is value to email append in certain circumstances. For those businesses that focus on the quality of the match and the Recency of the email address the future looks good.

Jed; glad to hear email append is working for your business. The concepts I discussed in the post are simply the sort of questions that link the exercise of email append with the revenue it is likely to generate. Any direct marketing activity should be linked to a measurable ROI and before embarking on the exercise, the marketer should be aware of KPI’s that will indicate success. My main point is that an email append project that will only increase the size of your data base and not the response from it, is a waste of time. I would suggest that the clients you have, that regularly return for repeat orders, are doing so because they have decided they get an adequate return on investment.

over 6 years ago


dulce johnson

Where did they get my email address or mobile number from? Yes. I agree. This is always the question. Even I ask this question every time I got an email from people that I didn’t know. So, I guess better introduce your name or the company you work for in order to gain their trust and give you their consent.

almost 6 years ago


jelly andrews

It is really important to have a constant communication with your customers. So I guess this email append services is a big help in making your business rolling.

almost 6 years ago


Reeves dominik, CEO at pioneerlists.com

Great work, Email appending is a process where the company collects their customers email-id to keep a healthy business relationship through just sending some offers or newsletters etc. but this should be done with the customers interest and the customer should be made aware of what they are getting themselves into. to know more on Email appending and to get a genuine Email appending services with the customer's knowledge visit http://www.pioneerlists.com/data-appending/email-appending

over 4 years ago


Andrew Jordan, Marketing at Smt Vendors

Hi...! Email append surely has its worth. But when purchased from Quality Data list providers.

In this on-going B2B competition, every business should have their target audience data base to contact them much before competitors do.

I run B2B company, since 2004. I have come across many data base providers like www.infousa.com , www.reachmarketing.com etc.., but none of them fulfilled my needs.
Recently a company named Gilbert Data (www.gilbertdb.com) helped me over come my target reach issues.
I highly recommend Gilbert Data.

about 1 year ago


John Lamason, Owner at Lead List Data

The entire process of email appending ensures that the messages of yours are received by the correct customers that have active and using email addresses.
Here is a similar article i really found useful https://leadlistdata.com/2018/02/email-appending-best-practices/

4 months ago

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