6 Ways to Develop Smart List Hygiene Practices for Your Email Program




Working on email deliverability issues for the last 3 years, one particular0 issue that keeps cropping up is the hygiene of the mailing list.  We once had a brand ‘X’ which was an upcoming e-commerce unicorn. They had a great, interactive website with a single opt-in subscription to their e-newsletters. They had social plugins installed and typos were corrected automatically within the subscription field. 

They thought they were collecting genuine email IDs. 

Their marketing team was excited to promote their products to their mailing list from their in-house setup.

That’s when the disaster started to unfold...

Initially, on starting their email program, they got a surge of spam complaints. Then came an increase in unsubscribes and by the end of the first month, 25% of their mailing list had churned out. There were bounces as well. But the issue that hit them the most was the eventual block-listing by Spamhaus. 

If they were collecting genuine ‘opt-in’ data:

  • Why was the mailing list churning out? 
  • Why did the delivery IP get blocklisted? 

That’s when they realized that something was amiss and they approached us for smarter delivery.  

After analyzing their data collection and list maintenance practices, we came to the conclusion that the brand marketing team lacked a smart list hygiene plan.  

That’s where we worked with them to dig deeper into their mailing list and come up with some insights. In this post, I talk about the challenges you face when you don’t have good list hygiene. Then we will look at how to implement smart strategies and create a firm data policy to educate your team. In the end, we can see how the brand ‘X’ received the benefits of investing in a healthy email list.       

So let’s first get to the crux of the issue. 

Are you checking up on your list hygiene?   

Brand marketers set up the verification and validation of their email ids but they ignore the importance of maintaining a clean mailing list.  Just because you have an email verification service does not mean that your list has 100% genuine subscribers. If it was that easy, no genuine senders would have got into blocklists

The verification will just tell you if those collected email ids are valid or invalid. But sometimes the email ids signed up could look valid but they could end up being bot sign-ups, fake email ids, typos and worst-case scenario - spam traps

Mailing to these ids could land your IP into one of those dreaded email blocklists.     

For a marketer, a lack of a list hygiene plan could sting harder if ignored. It could even result in being a show stopper for your email activity like we saw with brand ‘X’. 

This is where having a basic data scrubbing policy for your list will improve the quality of engagement, deliverability, and conversions. 

As Chad White from Oracle says “ A healthy list is a productive list.” So a basic list hygiene plan can improve the productivity of your list considerably and keep all the troubling issues at bay. 

Not convinced? 

Let’s look first at what kind of issues can crop up, if a marketer does not pay attention to the hygiene of their mailing list.

Lack of attention to your list spells trouble:

The marketing team of brand ‘X’ was confident that if users sign up to their email list then they must be genuine human users. 

It turned out to be a different story.

The following issues cropped up for the brand as they proceeded to ignore their list hygiene:  

  • Poor email delivery issues

Like brand ‘X’, marketers are always looking out for email delivery services that ensure 100% delivery of all their emails.

When they started mailing to their email list we realized that the actual delivery was only 90% of the total list. What that meant was 10% of the list was not deliverable. There were a lot of soft and hard bounces as well so clearly there were some email ids in the list which were either fake or invalid. 

Regular hard bounces from a domain/IP create red flags for the mailbox providers which essentially shows them that you are mailing to some users which don’t exist and hence raises suspicions of ‘list buying’, ‘mass spamming’. 

When this becomes a regular occurrence, MSPs(Mailbox Providers) heavily punish you by downgrading your sender/IP reputation and getting your domain in their “monitoring list". 

  • Bad sender reputation

With bad email delivery, brand ‘X’ also encountered a sliding sender reputation with major MSPs like Gmail punishing the poor hygiene of the list. MSPs are not happy when you send irrelevant content to your users.

Now the brand had an issue with email ids which received those emails and reported them to spam. The rising complaint rate coupled with the unsubscribes gave further indication to MSPs that not only was the brand mailing to invalid ids but also to disinterested users who didn’t want to receive these emails. 

Sender reputation is an indication of how your email program is faring with the MSPs and if it slides down, their spam filters start putting your emails into the junk box. 

This leads to a major problem, a wormhole of bad email deliverability.

  • Email deliverability issues

It is no wonder that poor sender reputation coupled with a disengaged list contributes to poor inboxing performance. As stated earlier MSPs monitor subscriber engagement on a daily basis. Hence, if the user ignores your emails, MSPs will start putting them into spam folders after a period of time.

The brand had witnessed reduced email deliverability within the first month with Gmail IPR at 30%, Yahoo IPR at 60%, and other MSPs were fairly low at 50%. Their reluctance to improve their email list and pause mailing for a while further downgraded their deliverability health. 

With 25% of the list churning out, alarm bells were running through their marketing team. 

The final KO punch was delivered when their delivery IPs were blocked by Spamhaus. 

  • Dreaded email blocklists

Not all blocklists on the internet affect your email delivery. But the major ones are monitored even by MSPs and hence cause an immediate consequence.

If a major blocklist sees suspicious spam emanating from your delivery IP/domain then your emails can be blocked with mailbox providers till you get them delisted. The delisting process is long and can take several days to even weeks. Your IPs/domain will remain blocked till then. 

That’s a potential loss of revenue for a brand that depends on email marketing for the majority of sales and web traffic.

Mailbox providers as well as anti-spam agencies like Spamhaus monitor your IPs even after they get delisted as they have been found to deliver spam in the past.

Blocklisting brought a halt to the activities of brand ‘X’. Now the matter had gone out of their control and they had to rely on some smart strategies from our consulting team to improve their email performance.  

So how does a marketer start working on their list hygiene?

It all starts by digging deep into your mailing list and doing some repair work on the quality of the database you have. 

The following are some of the data strategies we worked on with the marketers of brand 'X' to help them develop a productive list.

  • Develop a list scrubbing policy

Having a proactive attitude towards emailing to clean data could avoid major issues with your email program in the future.

A smart marketer needs to develop a list scrubbing policy.

  • Fix the typos in your subscribed email ids

eg: “gamil.com” instead of “gmail.com” or “yuhoo.com” instead of “yahoo.com” is very straightforward. 

  • Remove spam addresses 

eg: abc123@gmail.com or 123456abcdef@hotmail.com are obviously fake or they are potential honeypots. Mailing to these addresses is your one-way ticket to email delivery issues. 

  • Remove suspicious addresses

eg: dontspamme#$@domain or iamspammer123#*@domain. Such weird combinations of letters and numbers are red flags to avoid mailing to them.

Suppress such ids from your regular list. 

  • Protect from bot signups with CAPTCHA forms

There are increasing cases of bots used to sign up thousands of new ids to a mailing list. These could be done by spammers to mail to their list or some fake addresses.

 If this activity is not monitored on your website it could lead to a case of “list bombing” - your email list gets filled up with fake or spammy addresses causing serious list hygiene and delivery issues. Always use CAPTCHA forms to verify the users signing up for your newsletter. 

Monitor the average sign-up rate to your website and in case of anomalous huge spikes to subscriptions, always check if these ids are verified and validated. 

  • Check for disposable addresses

There are some services that provide temporary email addresses. Uninterested users who don't wish to check your emails will provide such ids.

eg: <username>@mailnator.com. Remove them from your list as they won't engage. 

  • Suppress your screamers from regular campaigns

If you sent a campaign to a small segment of users with a definite goal. You failed to get any good open rates from them (it happens!), but you also check Google Postmaster and you see a huge spam complaint rate. This means a majority of those users reported your emails as spam. They were either not interested in the campaign content that you sent but now they are also irritated with your brand emails.

It is very important to check who engages and who complains about your mailing list. 

When this happens, it is safe to park these segments of users under suppression for the next few campaigns. Reach out to them with a simple feedback campaign asking for what kind of content they will like to receive and if not just remove them from your list. 

A healthy list is one with an effective sunset policy.

  • Introduce double opt-in verification for your email newsletter

Though double opt-in is not a foolproof way of confirming the authenticity of an email address, it is still a substantial upgrade on single opt-in. It also saves a lot of time for the marketer to verify and validate the authenticity of these email ids.

If a user provides a confirmed opt-in by performing a 2-time verification then, rest assured you do have a genuine subscriber on your list. It helps to know if you are mailing to an interested user and double opt-in is a good way to ensure that. 

  • Watch out for blocklistings regularly

As a marketer, you should have clarity over the state of your delivery IPs and their hygiene. Not all of the blocklists of the internet that are presently monitoring the emails have a direct consequence on your program. But there are some major blocklists like Spamhaus, Spamcop, RBL, Invaluement etc. that could get your emails blocked.

You need to have a tool like the blocklist checker or MXToolbox which can provide you the details of the blocklisting when it occurs. Ignoring these blocklists will prove fatal for your email activity. The block lists generally inform your IT/system administrator about the listing but you can be proactive and check the status of your delivery IPs occasionally. 

Be smart and informed about your email infrastructure.  

  • Keep email as primary key for your database

Brand ‘X’ before working with us used to receive complaints from their users of receiving the same email multiple times. This was a classic case of duplication.

On further study of their CRM we came to the result that the primary key of the database was the mobile number and it was possible for a single user to have multiple numbers. The multiple numbers were tied to a single email id hence, one email was used to receive as many email copies as their unique mobile numbers. 

Hence we suggested the brand make a customer email id as their primary key to avoid sending duplicate copies to the same user, getting them annoyed.  

This tactic should save you from a lot of spam complaints.

  • Educate your team with a data policy document

Now once you have prepared a list scrubbing policy, document it and provide it to your entire team. Refer to the document to educate your team members and marketing clients on list hygiene and data maintenance policies.

Once you start keeping this data policy central to maintaining a list you will be surprised at the reduction in the number of data-related issues.

The email data policy should contain details on the following pointers:

      • How does the brand collect email ids from their newsletter/website signups? 
      • Keeping the email verification double opt-in.
      • Verification and validation process details.
      • List cleaning activity to be done every month.
      • Provisions for countering bot signups, spam traps, fake IDs, etc. 
      • An effective sunset policy for the list specifying the time period. 
      • Blocklisting and delisting process.
      • (If you use an Email service provider then the heavy lifting will be done by them in this regard
      • List segmentation process to be done according to user preferences, engagement activity, transaction history, etc.  

A basic email data policy like the above will ensure that the entire team is educated on good list hygiene practices. They will also have a better idea to troubleshoot issues when they arise in the future. 

Benefits of having an impeccable email list:

The following are some of the benefits that brand ‘X’ received when they implemented the above list hygiene strategies:  

  • Improved delivery and user engagement

When you clean your list regularly, the number of email ids that are bad or undeliverable will become minimal. This will mean that you will be targeting the valid email ids who will actually receive your emails. 

This will increase your delivery percentages and keep you away from bounces and bad reputation.

Mailing to a clean list will also improve your engagement metrics. More users who have a genuine interest in opening your promotional material will be able to receive them, improving your open and clicks.

Regular high engagement is an overall sign of a healthier email program.  

  • Reduced spam complaints and  improved deliverability

One of the primary benefits of mailing genuinely engaged subscribers is the minimal spam complaint rate you receive.   

Fewer spam complaints mean fewer deliverability issues as MSPs like Gmail strictly look at your domain complaint rate to gauge negative and positive signals from your subscribers. 

We saw earlier that for brand ‘X’, their block-listing issue led to inboxing issues. Well, once they scrubbed their list and made sure it contained clean email addresses, we saw an uptick in their inbox placement. 

Mailing to your engaged audience leads to a higher subscriber engagement. This is one of the primary reasons MSPs look after in their decision-making of placing emails in the inbox or spam folder. 

Targeting a clean and engaged list boosts your deliverability.

  • Removes marketing outliers & helps you make informed decisions

The problem with temporary or spammy IDs is that these addresses could actually engage with your emails and appear as behavior within your email metrics. This skews your email metrics and prohibits you from making appropriately informed decisions when it comes to evaluating email campaign effectiveness. With a clean and productive list, the issue of outlier IDs is minimum and may not be noticeable.


After list scrubbing, there could still be 5-10 outlier IDs in your list of say 15,000 ids valid subscribers. The performance of the majority of your email list will shadow these outliers and help you gain cadence regarding conversion rate, email ROI, etc.             

  • Building brand affinity and audience 

We have mentioned earlier that a host of issues crop up if you have a poorly performing email list. This could lead to blocklistings and your emails landing in the spam folder.

Few people will hear from your brand

Observing regular list hygiene and scrubbing activities will mean better deliverability as stated above. That leads to more users receiving your emails in their mailbox and actually reading them! 

Brands need to keep targeting indoctrination messages to their customers during their life-cycle. That would mean an increased affinity with your brand and its voice. 

Good quality service and products from your brand also leads to ‘spread of word’ publicity which will ultimately lead to a larger audience receiving your messages. 

  • Improved email ROI and conversion rate

Can following good list hygiene practices have an impact on your revenue? 

You bet it can! 

 When you start targeting an engaged audience for your campaigns, naturally, your conversion rates will improve as compared to before. Of course, you will have to educate your audience on why they need your services and your promotional messaging needs to be on point for that to happen.

Cleaning your list will also help reduce the delivery to neutral and invalid ids. That will mean a significant decrease in email volumes leading to a better cost-effective program.   

Increased conversions coupled with the reduction in delivered email ids will see an increase in your ROI. It will remove investment in delivering to bad ids and reduce your marketing budget with your ESP gradually. 

Improved sender reputation will provide accurate metrics for your decision-making. 

In a nutshell, a clean email list will provide better revenue, engagement, and inboxing. 



Following the above tactics to maintain your list hygiene will go a long way in reducing the data-related issues with your email program. 

It will improve your:

  • Email delivery and deliverability
  • Engagement and performance
  • Reduce spam complaints and avoid email blocklists
  • Increase your email ROI and conversions

Maintaining list hygiene is key to proactively avoid serious issues which can cause your program to come to a halt. 

So marketers need to start analyzing their list deeply as it has clues to uncover the loopholes which stop your program from getting to the next level. 


Author Bio


Tejas Pitkar is a product marketer and also handles Industry Relations at Netcore Solutions – Asia’s largest ESP.

He likes writing blogs, sharing the email knowledge, and making thought provoking videos on all things email on the youtube channel - “Email Talk”.

In his personal time, he enjoys hiking, backpacking, reading books, and drinking his favorite Chai.

You can reach him via his handles: 

Linkedin: https://www.linkedin.com/in/tejas-pitkar

Twitter: https://twitter.com/TPitkar

Youtube:  https://www.youtube.com/channel/UCQiDeo9rkrzpmazGmG5UOBw/videos


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