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Sending an email

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Updated at March 28, 2025

In Yandex Cloud Postbox, you can send an email using the AWS CLI or from your email client over SMTP.

Getting started

  1. Create a service account in the folder as the address. If you create the service account and address in different folders, you will get an error when attempting to send an email.
  2. Assign the postbox.sender role to the service account.
  3. Create a key for the service account:
    • To send an email using the AWS CLI or via SMTP with password authentication, create a static access key. Save the ID and secret key to a secure location. You will not be able to view the secret key parameters again after you close the window.
    • To send an email over SMTP with API key authentication, create an API key. When creating an API key, set the scope for yc.postbox.send. Save the secret key you got in a secure location. You will not be able to view the secret key parameters again after you close the window.

Send an email

AWS CLI

  1. Install the AWS CLI.

  2. Set up the AWS CLI:

    1. Launch the interactive profile setup: 
      aws configure
    2. Specify the previously obtained key ID of the postbox-user service account: 
      AWS Access Key ID [****************ver_]: <service_account_key_ID>
    3. Specify the previously obtained secret key of the postbox-user service account: 
      AWS Secret Access Key [****************w5lb]: <service_account_secret_key>
    4. Specify the ru-central1 default region name: 
      Default region name [ru-central1]: ru-central1
    5. Specify JSON as the default format for output data: 
      Default output format [None]: json

  3. Prepare two JSON files:

    • destination.json: File with a list of destination addresses:

      {
  "ToAddresses": ["test@example.com"]
}

    • message.json: File with the subject and content of the email:

      {
  "Simple": {
    "Subject": {
      "Data": "Test message",
      "Charset": "UTF-8"
    },
    "Body": {
      "Text": {
        "Data": "Test message. Hello!",
        "Charset": "UTF-8"
      }
    }
  }
}

  4. Send an email using the AWS CLI:

    aws sesv2 send-email \
  --from-email-address mail@example.com \
  --destination file://destination.json \
  --content file://message.json \
  --endpoint-url https://postbox.cloud.yandex.net

  5. Check the mailbox specified in destination.json for the email.

SMTP

You can send emails via SMTP with authentication based on a service account's API key or a password generated from a service account's static access key.

  1. In the SMTP server settings of your email client, specify the following parameters:

    • Server name: postbox.cloud.yandex.net.
    • Port: 587.
    • Username: API_KEY.
    • Password: Secret part of the created API key.

    Note

    Your email client must support the STARTTLS extension to encrypt emails you send.

  2. Send an email using your email client and make sure the specified recipients receive it.

  1. Get a password using the previously created static access key of the service account. To do this, run the generate.py script. Use Python 3 or higher.

    python generate.py <service_account_secret_key>
    generate.py
    #!/usr/bin/env python3

import hmac
import hashlib
import base64
import argparse
import sys

# These values are required to calculate the signature. Do not change them.
DATE = "20230926"
SERVICE = "postbox"
MESSAGE = "SendRawEmail"
REGION = "ru-central1"
TERMINAL = "aws4_request"
VERSION = 0x04


def sign(key, msg):
    return hmac.new(key, msg.encode("utf-8"), hashlib.sha256).digest()


def calculate_key(secret_access_key):
    signature = sign(("AWS4" + secret_access_key).encode("utf-8"), DATE)
    signature = sign(signature, REGION)
    signature = sign(signature, SERVICE)
    signature = sign(signature, TERMINAL)
    signature = sign(signature, MESSAGE)
    signature_and_version = bytes([VERSION]) + signature
    smtp_password = base64.b64encode(signature_and_version)
    return smtp_password.decode("utf-8")


def main():
    if sys.version_info[0] < 3:
        raise Exception("Must be using Python 3")

    parser = argparse.ArgumentParser(
        description="Convert a Secret Access Key to an SMTP password."
    )
    parser.add_argument("secret", help="The Secret Access Key to convert.")
    args = parser.parse_args()

    print(calculate_key(args.secret))


if __name__ == "__main__":
    main()

  2. In the SMTP server settings of your email client, specify the following parameters:

    • Server name: postbox.cloud.yandex.net.
    • Port: 587.
    • Username: ID of the previously created static access key.
    • Password obtained in the previous step.

    Note

    Your email client must support the STARTTLS extension to encrypt emails you send.

  3. Send an email using your email client and make sure the specified recipients receive it.

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