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 of 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 to 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 for performing 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 requires 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 offers 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.

Import CSV
Import CSV

Datablist reads CSV files and Excel files. Your first rows will be read to detect the encoding used. If you see weird characters on the detected headers or later when importing, create another collection and try to import your CSV using another encoding.

Select File to import
Select File to import

Datablist will read the columns and it will show you a mapping page. If your email addresses are valid, the data type will be Email. It will add some validation to your data edition later on Datablist.

Check property types
Check property types

Here is a video of the full process:

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.

When importing another file, a mapping step will be shown. In this step, you will map your collection properties with your CSV columns. With this mapping, your new data will be added to the existing properties.

Mapping when importing other files
Mapping when importing other files

Step 2: Find and merge 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 duplicate rows.

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

Use Datablist "Duplicates Finder" features by clicking on the "Duplicates Finder" button in the clean menu.

Run duplicates finder
Run duplicates finder

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.

Duplicate Results
Duplicate Results

If duplicates are found, several actions are available:

  • Merge or consolidate duplicate items
  • Remove duplicate items
  • Edit them

Datablist has an automatic algorithm to dedupe your data. Please visit our documentation to learn more about deduplication.

After the automatic merge, finish the cleaning with the manual merging assistant. 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 the "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.

Check this video for the whole process:

Detect and remove duplicates

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 registered 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 4 verifications:

  • Email syntax analysis
  • Domain MX records check
  • Disposable providers check
  • Is the email address a Business Email or from a generic provider (Gmail, Yahoo, etc.)

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 flag addresses without the at sign (@), with invalid domains, etc.

Check domain MX records

The second check is to detect if the domain can receive emails. 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.

Check disposable providers

The third 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 if the email address is a business email

Another information available with Datablist "Email Address Validation" enrichment is whether the email addresses are business email addresses or generic ones.

A business email address has a company domain (such as When segmenting your contacts to build your lead lists, spotting the business email addresses will help you in the lead scoring.

Datablist maintains a list of all the generic email providers. It compares each email domain with this list. The email address is labeled as "Business Email" when the domain doesn't belong to the list of generic email providers.

Perform cleaning on your collection

Performing an email list cleaning on Datablist is simple. Just click on the "Enrich" menu and select the "Email Address Validation" enrichment.

Click on "Enrich"
Click on "Enrich"
Select Email Address Validation
Select Email Address Validation

Once you have selected "Email Address Validation", a drawer opens on the right to configure the enrichment.

The configuration takes 2 steps:

  • The configuration of Settings and Input Properties
  • The configuration of Output Properties to define where to store the results from the enrichment
Enrichment options
Enrichment options

Settings and Input Properties


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.

👉 Click on "Continue to outputs configuration" to move to step 2.

Output Properties and Run Settings

Outputs configuration
Outputs configuration

The "Email Address Validation" enrichment returns 4 values:

  • Valid Email - A Checkbox (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.
  • Business Email - A Checkbox to know if the email address is a Business Email or from a generic email provider
  • Processed - A Checkbox to flag if an item has been processed. It is useful to filter your email list and avoid running the enrichment twice on the same email addresses.

⚠️ You must configure the output properties to create new properties in your collection. Or map them to existing properties.

If you are running the enrichment for the first time, click on the + button on each output property to add the result properties to the collection.

Properties to be created are displayed on the right of your columns.

Add output property to your collection
Add output property to your collection

When the outputs are mapped with properties to store the results, click "Run on first 10 items". Before running the enrichment on all your items, Datablist processes the ten first items. Errors and invalid configurations are easier to detect from those first results.

Run on the first 10 items
Run on the first 10 items

If the results are correct, click "Run the enrichment on all items" to resume the process.

Email verification results
Email verification results

Here is a video of the process (this is an old Datablist version, the email verification enrichment is now accessible from the "Enrich button"):

Verify email addresses for free

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

Find and remove email aliases

Google Gmail and Microsoft Outlook (among others) let users create alias email addresses by adding +something to the email username.

For example, the Gmail email addresses and are linked to the same inbox.

Each alias is valid, and passes the validation test, but still impacts your marketing cost and deliverability score.

Here are a few steps to remove extra alias email addresses from your contacts list.

First, filter all email addresses with a + character.

Open the filter modal
Open the filter modal
Filter the Email property with +
Filter the Email property with +

Then, open the Find & Replace tool in the "Clean" menu.

Find & Replace
Find & Replace

Select the option Match using regular expression, and search on your Email property. And write the following search pattern:


And write this string in "Replace with":


This Regular Expression removes the +string from email addresses.

Regular Expression
Regular Expression
Find & Replace preview
Find & Replace preview
Find & Replace results
Find & Replace results

Then you can remove the filter and run the Deduplication Algorithm again on your email addresses database. Check how to deduplicate your contacts list above.

The deduplication step removes extra email addresses when a version exists without the alias, and keeps the email address when it is the only address.

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, import the second CSV file and perform a join operation into the same collection.

The common property is the Email property. You will perform a "join operation" on the Email property.

During the import of the CSV files with the unsubscribed email addresses, create a new property to store the "Unsubscribed" column (click on the "+" during the mapping).

Create new property for Unsubscribed column
Create new property for Unsubscribed column

Map the "Email" column with the "Email" property if not already done. Then enable "Join on property" on it.

Join on the Email
Join on the Email

In the next step, you have to configure how Datablist will perform the join operation on the CSV file.

  • Import all rows and match when possible - If an email address from the Unsubscribed file doesn't exist in your collection, a new item will be created.
  • Import only matching rows - This is the recommended option here. If an email address from the Unsubscribed file doesn't exist in your collection, the email address will be skipped during the import.

The "Merging Mode" is to define how to merge conflicting data. This is useful when you update your collection and already have an "Unsubscribed" property that you want to update.

Define join options
Define join options

After the import, the new property "Unsubscribed" will appear. You can filter on the property and remove the contact items.

Email verification results
Email verification results

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. With this property option, Datablist will automatically deduplicate and merge your contacts on data import.

Define unique option for Email property

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.