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A emailing python library for emailing from alternative domains - DNS entries etc need to be assigned (not used for spamming).

Project description



smtpymailer is a versatile Python library designed to simplify the process of sending emails in python. It supports and validates DKIM, DMARC, and SPF records before sending emails to avoid being marked as spam, so it is ideal for sending emails from your own mail server but the sender is an alternative domain.


  • Login to any mail server of your choice (I maintain a postfix server for outgoing mail only, so replies are still directed to the users normal inbox).
  • Send emails from different domains, provided the correct DNS settings are in place.
  • Validates DNS settings like DKIM, DMARC, and SPF before sending emails to avoid being marked as spam.
  • Full email functionality including To, CC, BCC, Reply-To, and attachments.
  • Adds attachments with the correct MIME type.
  • Optionally converts url tags to inline attachments CID attachments or Base64 encoded img sources, this is controlled by data attributes data-inline or data-base in the img tag.
  • Supports sending string HTML content, Jinja templates, or plain html files.
  • Automatically converts HTML to plain text for email clients that do not support HTML.
  • Supports environment variables and .env files for mail server settings.


Install the package using pip:

pip install smtpymailer



Create an instance of SmtpyMailer with your sender email and name. The mail server details can be passed as keyword arguments or sourced from environment variables or a .env file.

Environment Variables

The following environment variables can be set or added to a .env file in your project root. Alternatively you can pass as **kwargs to the SmtpyMailer class but this is not advised.

  • MAIL_SERVER: The mail server hostname.
  • MAIL_PORT: The mail server port.
  • MAIL_USE_TLS: Whether to use TLS or not.
  • MAIL_USERNAME: The mail server username.
  • MAIL_PASSWORD: The mail server password.
  • MAIL_DKIM_SELECTOR: The DKIM selector of the domain you are sending from. (This is used to validate your ability to send from the domain).
from smtpymailer import SmtpMailer
mailer = SmtpMailer(sender_email="", sender_name="Foo Bar")

Sending an Email

Use the send_email method to send emails:


  • recipients: Single recipient email or a list of email addresses.
  • subject: Email subject.
  • cc_recipients: (Optional) Single or list of CC email addresses.
  • bcc_recipients: (Optional) Single or list of BCC email addresses.
  • reply_to: (Optional) Reply-to email address.
  • attachments: (Optional) Single file path or list of file paths for attachments.
  • html_content: (Optional) HTML content of the email (not required if using a template)
  • template: (Optional) Template file path (using jinja), it can be just a plain html file.
  • template_directory: (Optional) Single or list of template directories.
  • **kwargs: Additional arguments for jinja template, if needed.


  • Send a simple email with a subject and html content.
from smtpymailer import SmtpMailer
mailer = SmtpMailer(sender_email="", sender_name="Foo Bar")
mailer.send_email(recipients="", subject="My test email", html_content="<h1>Hello World</h1>")
  • Send to multiple recipients, one CC, with an attachment, and a jinja template with kwargs.
from smtpymailer import SmtpMailer
mailer = SmtpMailer(sender_email="", sender_name="Foo Bar")
template_data = {"name": "Foo Bar", "message": "Hello Foo", "url": ""}
mailer.send_email(recipients=["", ""], cc_recipients="", subject="My test email", template="template.html", template_directory="./templates", **template_data)

Sending From Alternative Domains

You can send emails from alternative domains by setting up the correct DNS settings. Here's how to do it. Alt Domains Documentation


This project is licensed under the MIT License.


  • Change the way the send function's alter_img_src parameter works. It should AUTODETECT img elements with data-inline or data-base attributes instead.

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