Captain Verify Documentation

Getting Started

CaptainVerify allows you to check the validity of your emails by sending them as a list or using the API directly in your application. Here are the steps to start:

Step 1: Create a free account CaptainVerify

CaptainVerify offers checking emails 100 free for opening the account (on demand). If you need more, find on the homepage our price. Click here to create your free account.

Step 2: Validate your emails

You are now ready to upload a list (csv or txt file) to check emails and / or to incorporate API. Feel free to send to support any of your questions.

How CaptainVerify works

CaptainVerify will check the validity of your emails using the SMTP protocol. It's the same one you use without necessarily knowing when you send your emails. CaptainVerify does not send email to verify, but step by step will query the remote system, such as Gmail. Who will tell us if the email request does exist. In addition to this final check, we check the existence of the upstream area, where an associated SMTP server in this field, and more.

While this approach may seem simple, it is actually surprisingly complex that we begin to want to check more than 10 emails. The email providers are implementing a lot of measures to make sure that the request is legitimate. This is why many companies use our system and benefit from our experience.

Terminology: Email status

Result Description


The email is valid, you can send it without problems.


The email is invalid, delete it from your database, or deny entry if you use the API


The remote server provider does not respond in time.
This means that we have not received a clear answer for technical reasons beyond our control (slow / bad configuration of the server, antispam protection so that the verification changes to "unknown". Unknown checks are re-credited.

Qualification email

Result Description


The supplier is free (Gmail, Yahoo, etc ...) is a good sign if your database is BtoC


Users of this email has a role, for example contact@ or info@ or posmaster@.
This means that this email is not addressed to anyone in particular, avoid sending this kind of emails.


The email is valid, but disposable after a short time it will not be possible to contact the user.


This email address seems to belong to an organization that tracks spam, it is very risky to send and no real person is behind this email

Details: understand why a check is unknown

Details Description


Error: The server says the check failed


Smtp error: the server reported an internal error from the remote server


The smtp session was closed before checking the email


The verification of the email failed and the email does not seem to exist


Rejected: delivery failure


Relay error: delivery failure


Antispam technology blocks verification progress


Email is disabled: Suspended / Disabled / Limited


The domain mail server is not installed or is incorrect


Ok for all: the remote mail server accepts any email


The mail server is dead


Syntax error in the email address


Failed to check email, but no information on why

Security and Privacy

Your email is sensitive, you belong and must remain private and secure. CaptainVerify not share or never will rent this information to third parties. All information passing through CaptainVerify are encrypted via SSL, it is the same protocol used for secure financial transactions.

During a check list, once your file downloaded and validated, it will be encrypted and a unique password will be asked to open it. Similarly, when using the API, the emails you want to check go through https (SSL) and are therefore not readable in the clear over the network.

Email List Validation

Step 1: Import a list

Your file containing the emails must be in CSV format ideally with as column separator and the comma as utf8 encoding. Make sure you have a file (csv or txt) that meets the following conditions:

  • the mailing list should contain an email per line
  • the first line should contain a field named but it is optional
  • Your file must contain only one column with the email addresses. Additional columns will be automatically deleted.

exemple csv

You cannot have additional columns in addition to the email column, the file will be returned to you in addition to the validity information of the email. To send your file, click on "Browse" or simply drag the file within the framework provided for this purpose.

Step 2: Format Control

A compliance check will then be made to your file for the presence of emails and see if the format is correct. Once this step, you will be notified by email and you can then start checking the file.

Step 3: Start the verifications

To start checking the file you must click Start. If you ever do not have enough credits to fully check the file, processing will stop when your credits will be 0. You can then purchase the missing and start a new verification credits.

Start Verification

Step 4: Retrieve the list

download list

Once verification is complete you can download the file (XLSX) with different information or your entire list or only a list of valid emails, invalid, or those whose status is unknown. For each line, the columns Statut, Free, Disposable, Risky, Role, Did_you_mean and Detail are added. Warning, your list is encrypted and protected by a password, it will appear near the button "Download". Once you have recovered your list, we recommend you delete it from the queue.

Your file will be as in the example below.

verify list


With the CaptainVerify API, you can integrate the verification email in your own applications. This allows you for example to check whether your users well informed before a correct email registration.


An account is required to generate key for the API, it is these that will give you access to the service.

The request

To make a request to the API, just call the GET protocol this URL:

Replace by your email to check

The answer

A json table will be returned with these variables:

Variable Possible value


true, false
If problems authentication, exhaustion of your credit success return false


default : null
When success is false an error message will be sent.


Credits available on your account


The email you want to check


The email normalized removing tags for gmail... will be


true, false
If the user of the email has a role, eg


true, false
If the email provider is free, eg


true, false
If the email provider is disposable, ie if the email has a short service life


true, false
If the email provider is a fight against spam service and not a real user


default : null
If for example the email to verify the API is will send you a proposal as


valid, invalid, unknown
The status of the email. if all your credits have been exhausted, the unknown status will always be returned, so as not to block your application.


null, error, smtp_error, antispam_system, email_disable, ok_for_all...
Understand why an audit is unknown.

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