Email lists are the start of any email campaign and newsletter management. However, a list can get messy from multiple merges or with user spammy behavior.

The benefits for cleaning your email list are:

  • Improve deliverability - Every email provider uses your sender score to determine where to route your emails. To avoid being labeled as SPAM and successfully reach your user, the first step is to avoid sending emails to non-existing addresses. A bad sender score is hard to revert, so better spend some time up-front and clean your list from unreachable email addresses.
  • Save money - Usually, you pay for each email you send. First, pruning your email list to remove duplicates and invalid addresses will save you money. Then, you need to remove all disposable email addresses that will never be read to keep only real emails.
  • Detect and fix typos - After the cleaning process, wrong email addresses will be flagged. Manually, you can find simple typos in names or domains and fix them.

Email list cleaning is an important part of any digital business and must be done regularly. Datablist is a perfect data tool to perform this cleaning process. Using this step by step guide, you will learn:

Datablist can be used without registration to view and edit CSV files. However, the email verification service that we'll use later require an account.

👉 Create your account for free 👈.

How does it compare to paid email cleaning services?
If you search for email verification services on Google, you'll find hundreds (thousands?) of them. Almost all of them charge a fee per email address. Datablist includes an email verification service and it is free. It is great and enough for simple email verifications. However, if you need deeper analysis or if you have to perform verifications on hundreds of thousands of emails, please use a paid email cleaning service.

Step 1: Import email addresses

Create a collection

The first step in the email cleaning process is to create a collection on Datablist in which you will pour your email addresses.

In Datablist, click the + to create a new collection. Give it a name (and an icon 😍).

Import your lists of email addresses

Now you have a collection, it's time to import your email lists: whether you have only one email list or several that you want to merge!

Datablist offers two options to import your data:

  • With CSV files
  • Using copy/pasting from a spreadsheet

Option 1: Import from CSV files

The CSV format is a simple standard to transfer tabular data between software applications. Every newsletter tool and digital marketing solution offer exports of your contacts in CSV files. CSV files are first-class citizens in Datablist.

See also our How to join CSV files by a unique identifier and How to remove CSV duplicates guides.

In this example, we will use a demo contact CSV file with three columns: First Name, Last Name, email. Download the demo file here.

To import your CSV file, click the "Import CSV" button and select your file. Datablist will read the columns and show you a mapping page.

Create a property with the + button for every CSV column. On property creation, select the data type for each column. Select Email for the email address column so Datablist can perform data integrity analysis.

Create a new collection and import CSV

Option 2: Import with Copy/Pasting

Datablist is compatible with copy/pasting from any spreadsheet. Just select the cells from your spreadsheet, go to your Datablist collection and use the Edit -> Paste from your browser or directly the Ctrl + v keyboard shortcut.

On pasting, Datablist will show you the columns and rows it has detected. To import a column, map it to an existing property or create a new property.

Warning: Only mapped columns will be imported!

Copy Pasting From Google Sheets

Import other contact lists if needed

If you are building an email collection from several sources, just import all your lists into the same collection. Just ensure all the list are mapped to the same properties.

Step 2: Find and merge duplicates

Detect and remove duplicates

It's common to have an email list built over time. The result is several email listings merged into one. Resulting in duplicates! If your list stores contact information like First Name, Last Name, etc. you might have contact information spread over several duplicates rows.

With all your email addresses in one place. The second step is to remove or merge duplicates entries.

Use Datablist "Duplicates Finder" features by clicking on the "Duplicates" button in the collection header (on the right).

In the configuration screen, you need to select how duplicates will be checked:

  • All Properties - Look for full items similarity: Two items would be considered similar when all of their properties match.
  • Selected properties - Two items would be considered similar when all of their properties match.

In our example, two contacts are duplicates if they share the same email address. So, pick the Selected Properties mode and select the Email property.

Run the duplicates check to see a preview of all duplicates found in the collection.

If duplicates are found, three actions are available:

  • remove duplicate items
  • edit them
  • merge (and consolidate) contacts.

To merge duplicate contacts, click on the "Merge Items" button on the left of every duplicate contacts group.

Merge contacts
Merge contacts

Datablist has a merging tool. On the right, a "Primary Item" is shown and on the left the remaining duplicate contacts are called "Secondary Items". Datablist elects the contact with the most data as "Primary item".

Eliminate duplicate rows in a CSV
Eliminate duplicate rows in a CSV

When possible, property values from secondary items are auto selected to be merged into the primary items. If several values conflict, you will have to make a decision and select which value to keep.

If the resulting "Primary item" suits you, click the Merge button to confirm the merge process. All the secondary items will be deleted to keep only one combined item.

Once all the duplicates have been processed, go back to the collection.

Step 3: Free email list cleaning

Now you have a collection on Datablist with all the email addresses and no duplicates, it's time to clean it!

You must be register to use the email verification service. Sign up (it's free). If you already have an anonymous collection, import it into your workspace.

What does the service check?

Datablist has a built-in free email verification service. This free service does 3 verifications:

  • Email syntax analysis
  • Disposable providers check
  • Domain MX records check

Email syntax analysis

The first check is to ensure the email conforms to the IEFT standard and does a complete syntactical analysis.

This analysis will flagged addresses without the at sign (@), with invalid domains, etc.

Check disposable providers

The second check is to detect temporary emails. The service looks for domains belonging to Disposable Email Address (DEA) providers such as Mailinator, Temp-Mail, YopMail, etc.

The current database lists about 3000 disposable provider domains and is updated regularly using this disposable domains list.

Check domain MX records

A valid email address must have a corresponding domain name with configured MX records. Those MX records specify the mail server accepting the email messages for the domain. Missing MX records indicate an invalid email address.

For every email address domain, the service checks the DNS records and looks for the MX ones. If the domain doesn't exist, the email will be flagged as invalid. If the domain exists and doesn't have a valid MX record, it will also be flagged as invalid.

Perform cleaning on your collection

Performing an email list cleaning on Datablist is simple. Just select the email addresses in your collection and run the "Email Address Validation" action.

Once you have selected "Email Address Validation", a drawer opens on the right with 3 sections: Settings, Input Properties, and Output.


Select "Check for MX-records in email domain" in the settings to analyze the MX records.

Input Properties

Select the property from your collection that contains the email address. In this example, the collection has an "Email" property that will be matched.


The "Email Address Validation" service returns 2 values:

  • Valid Email - A boolean (true or false) to indicate whether the email address is valid.
  • Error status - A text explaining why the email address is invalid when "Valid" Email" is false.

It's important to map the output properties to the collection to store the results.

Click the + on the right of each output property to add the result properties to the collection.

Verify email addresses for free

Once the service is done, analyze all invalid emails to detect easy fix typos.

Step 4: Remove unsubscribed emails

This last step is optional. You might have a dedicated list containing all unsubscribed emails that you want to remove from your main list. If your list with unsubscribed emails has a specific column like:

email           |     Unsubscribed     |     yes     |     yes     |     yes

It is possible to perform a join operation and add the Unsubscribed information to your contact list.

To do so, go to the properties configuration modal and select "Do no allow duplicate values" on the Email property. Because you set the Email property to be unique, your data will be merged into your collection resulting in a single list with the Unsubscribed property.

Define unique option for Email property

Then, simply import your unsubscribed email list in the Datablist collection using a CSV file or copy/pasting.

Don't forget to create and map the "Unsubscribed" column during the import.

Extra Step: Automatic merge duplicates during import

To prevent and merge duplicates automatically during the import process. Check the "do not allow duplicate values" option on the Email property (see video on step 4). With this property option, Datablist will automatically deduplicate and merge your contacts on data import.

During the import stepper, a merging option will be shown to configure how Datablist must deal with duplicates.

CSV Join - Merging Options
CSV Join - Merging Options

The merging option is important when your listing contains contact information in addition to the email address.

  • With Soft Merge, if a contact exists with the same email, it will not update properties with previous data (contacts already in the collection or the first contact found in the CSV). This is the default setting.
  • With Hard Merge, if data exists with the same email, it will update it.

If you have any feedback on this guide or if you have questions, please contact us.