seacucumber 1.5.2

A bird’s eye view

Sea Cucumber is a mail backend for Django. Instead of sending emails through a traditional SMTP mail server, Sea Cucumber routes email through Amazon Web Services’ excellent Simple Email Service (SES) via django-celery.

Why Sea Cucumber/SES instead of SMTP?

Configuring, maintaining, and dealing with some complicated edge cases can be time-consuming. Sending emails with Sea Cucumber might be attractive to you if:

• You don’t want to maintain mail servers.

• Your mail server is slow or unreliable, blocking your views from rendering.

• You need to send a high volume of email.

• You don’t want to have to worry about PTR records, Reverse DNS, email whitelist/blacklist services.

• You are already deployed on EC2 (In-bound traffic to SES is free from EC2 instances). This is not a big deal either way, but is an additional perk if you happen to be on AWS.

Installation

Assuming you’ve got Django and django-celery installed, you’ll need Boto 2.0b4 or higher. boto is a Python library that wraps the AWS API.

You can do the following to install boto 2.0b4 (we’re using –upgrade here to make sure you get 2.0b4):

pip install --upgrade boto

Install Sea Cucumber:

pip install seacucumber

Add the following to your settings.py:

EMAIL_BACKEND = 'seacucumber.backend.SESBackend'

# These are optional -- if they're set as environment variables they won't
# need to be set here as well
AWS_ACCESS_KEY_ID = 'YOUR-ACCESS-KEY-ID'
AWS_SECRET_ACCESS_KEY = 'YOUR-SECRET-ACCESS-KEY'

# Make sure to do this if you want the ``ses_address`` management command.
INSTALLED_APPS = (
    ...
    'seacucumber'
)

Email Address Verification

Before you can send email ‘from’ an email address through SES, you must first verify your ownership of it:

./manage.py ses_address verify batman@gotham.gov

After you’ve run the verification above you will need to check the email account’s inbox (from your mail client or provider’s web interface) and click the authorization link in the email Amazon sends you. After that, your address is ready to go.

To confirm the verified email is ready to go:

./manage.py ses_address list

To remove a previously verified address:

./manage.py ses_address delete batman@gotham.gov

Now, when you use django.core.mail.send_mail from a verified email address, Sea Cucumber will handle message delivery.

Rate Limiting

If you are a new SES user, your default quota will be 1,000 emails per 24 hour period at a maximum rate of one email per second. Sea Cucumber defaults to enforcing the one email per second at the celery level, but you must not have disabled celery rate limiting.

If you have this:

CELERY_DISABLE_RATE_LIMITS = True

Change it to this:

CELERY_DISABLE_RATE_LIMITS = False

Then check your SES max rate by running:

./manage.py ses_usage

If your rate limit is more than 1.0/sec, you’ll need to set that numeric value in your CUCUMBER_RATE_LIMIT setting like so:

# Rate limit to three outgoing SES emails a second.
CUCUMBER_RATE_LIMIT = 3

Failure to follow the rate limits may result in BotoServerError exceptions being raised, which makes celery unhappy.

As a general note, your quota and max send rate will increase with usage, so check the ses_usage management command again at a later date after you’ve sent some emails. You’ll need to manually bump up your rate settings in settings.py.

Routing Tasks

If you want to route Sea Cucumber task to different queues.

Add this to setting:

CUCUMBER_ROUTE_QUEUE = 'YOUR-ROUTE-QUEUE'

Then update the celery configuration for routes. Example celeryconfig.py:

CELERY_ROUTES = {
    'seacucumber.tasks.#': {'queue': 'YOUR-ROUTE-QUEUE'},
}

DKIM

Using DomainKeys is entirely optional, however it is recommended by Amazon for authenticating your email address and improving delivery success rate. See http://docs.amazonwebservices.com/ses/latest/DeveloperGuide/DKIM.html. Besides authentication, you might also want to consider using DKIM in order to remove the via email-bounces.amazonses.com message shown to gmail users - see http://support.google.com/mail/bin/answer.py?hl=en&answer=1311182.

To enable DKIM signing you should install the pydkim package and specify values for the DKIM_PRIVATE_KEY and DKIM_DOMAIN settings. You can generate a private key with a command such as openssl genrsa 1024 and get the public key portion with openssl rsa -pubout <private.key. The public key should be published to ses._domainkey.example.com if your domain is example.com. You can use a different name instead of ses by changing the DKIM_SELECTOR setting.

The SES relay will modify email headers such as Date and Message-Id so by default only the From, To, Cc, Subject headers are signed, not the full set of headers. This is sufficient for most DKIM validators but can be overridden with the DKIM_HEADERS setting.

Example settings.py:

DKIM_DOMAIN = 'example.com'
DKIM_PRIVATE_KEY = '''
-----BEGIN RSA PRIVATE KEY-----
xxxxxxxxxxx
-----END RSA PRIVATE KEY-----
'''

Example DNS record published to Route53 with boto:

route53 add_record ZONEID ses._domainkey.example.com. TXT ‘“v=DKIM1; p=xxx”’ 86400

Django Builtin-in Error Emails

If you’d like Django’s Builtin Email Error Reporting to function properly (actually send working emails), you’ll have to explicitly set the SERVER_EMAIL setting to one of your SES-verified addresses. Otherwise, your error emails will all fail and you’ll be blissfully unaware of a problem.

Note: You can use the included ses_address management command to handle address verification.

Getting Help

If you have any questions, feel free to either post them to our issue tracker.