django-email-hosts – Support for several SMTP configurations in a single site

Why?

Some projects may want to sent emails over multiple SMTP relays or smarthosts. Examples are sites running on multiple domains, e.g. info@example.com and info@example.org. It may be possible to use the same SMTP credentials for each sender address but if that isn’t possible django-email-hosts may be a good solution for the problem.

Usage

• Install: pip install django-email-hosts

• Configure: Add the EMAIL_HOSTS setting

• Use: Always explicitly use the SMTP connection returned by email_hosts.backends.get_connection

EMAIL_HOSTS

The keys of the EMAIL_HOSTS dictionary are defined by you and there’s no deeper meaning to them. The values are DSNs inspired by dj-email-url DSNs.

An example configuration (which is possibly nonsensical) looks like this:

EMAIL_HOSTS = {
    "sendgrid": "submission://USER:PASSWORD@smtp.sendgrid.com?_default_from_email=info@example.com",
    "mailgun": "submission://USER:PASSWORD@smtp.mailgun.com?_default_from_email=info@example.org",
}

This configuration creates two SMTP backends, one using sendgrid and one using mailgun. The _default_from_email is completely optional. If the email message’s from_email isn’t set (resp. is equal to the DEFAULT_FROM_EMAIL setting) it automatically defaults to the per-backend value.

email_hosts.backends.get_connection

The get_connection function expects a single key for the EMAIL_HOSTS setting above. Sending a single email using an explicit connection may look as follows, using the settings from above:

from django.core.mail import EmailMessage
from email_hosts.backends import get_connection

EmailMessage(
    "Hello",
    "World",
    to=["recipient@example.com"],
    connection=use_backend("sendgrid"),
).send()

get_connection currently silently returns the default email backend if the key doesn’t exist in the EMAIL_HOSTS dictionary.

Change log

Next version

0.2 (2022-02-07)

• Removed the functools.cache decorator from get_connection – constructing backends isn’t that expensive and the danger of memory leaks when misusing the connection management is worse.

• Removed support for the ssl_keyfile and ssl_certfile parameters since they are never returned by dj-email-url anyway.

• Changed the implementation to use documented APIs instead of undocumented internals of Django.

• Switched from dj-email-url to speckenv_django for parsing the email URL.

0.1 (2022-02-03)

• Initial release!