# Step 4: Email Verification

In this step, CSVgo determines whether each email address is:

* **Valid**
* **Invalid**
* **Catch-all** (unknown or risky at this stage)

This step focuses on **technical deliverability**, not assumptions or guessing.

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### What Email Verification Does

CSVgo performs a deep email verification process designed to reduce bounces and protect sender reputation.

Each email is evaluated using multiple technical checks to determine whether the address can receive email.

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### Verification Checks Performed

#### Duplicate Removal

Before verification begins, duplicate email addresses are removed automatically.

This prevents:

* Wasted verification credits
* Duplicate outreach
* Inflated list sizes

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#### Email Syntax Check

CSVgo checks that each email:

* Uses valid characters
* Contains a proper local part
* Includes an `@` symbol
* Has a correctly structured domain

Invalid syntax results in immediate classification as invalid.

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#### Domain and DNS Check

CSVgo verifies that the email domain:

* Exists
* Has valid DNS records
* Is configured to receive email

Domains without valid mail records are marked as invalid.

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#### SMTP Connection Test

CSVgo attempts to establish a connection with the recipient’s mail server.

The server response is used to determine whether:

* The mailbox exists
* The mailbox does not exist
* The server accepts all addresses (catch-all behavior)

This step is critical for real-world deliverability assessment.

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#### Greylisting and Retry Logic

Some mail servers temporarily reject verification attempts and require retries.

CSVgo accounts for this behavior by:

* Detecting soft responses
* Retrying verification automatically
* Avoiding premature invalid classifications

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#### Catch-All Detection

If a mail server accepts messages for non-existent addresses, the domain is marked as **catch-all**.

At this stage:

* The email is neither confirmed valid nor invalid
* It is classified as **catch-all (risky or unknown)**

These emails move to the next verification step.

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#### Disposable and Free Provider Detection

CSVgo detects whether an email address belongs to:

* Disposable or temporary email providers
* Free email services such as Gmail or Outlook

This information is stored for segmentation and campaign strategy decisions.

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#### Role-Based Email Detection

CSVgo identifies role-based addresses such as:

* info@
* admin@
* support@
* sales@

These emails are flagged so teams can decide whether to include or exclude them.

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### Verification Results at This Stage

After Step 4, every email is categorized as one of the following:

* **Valid** – confirmed to exist and receive email
* **Invalid** – confirmed not deliverable
* **Catch-all** – server accepts mail but mailbox existence is unknown

Catch-all emails are **not discarded**. They proceed to the next verification step.

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### Why This Step Matters

Email verification:

* Reduces hard bounces
* Protects domain reputation
* Improves inbox placement
* Creates a clean foundation for advanced verification

This step ensures only technically deliverable emails continue in the workflow.

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### Summary

In Step 4, CSVgo:

* Removes duplicate emails
* Checks syntax and domains
* Connects to recipient mail servers
* Identifies valid, invalid, and catch-all emails
* Prepares catch-alls for deeper verification

The next step focuses specifically on **catch-all verification** to recover additional deliverable leads.