Delaying the sending emails with Sendgrid and Django, SMTP api and send_at header

Question

I've spent a lot of time figuring out how to send email at a specified time in Django, so I am posting it with answer here to save others some time.

My use case is sending email during working hours. Using celery for that is a bad idea. But Sendgrid can send emails with a delay of up to 3 days. That's what we need.

Answer 1

That what I made:

from django.core.mail import EmailMultiAlternatives
from django.template.context import Context
from django.template.loader import get_template
from smtpapi import SMTPAPIHeader
def send_email(subject, template_name, context, to, bcc=None, from_email=settings.DEFAULT_FROM_EMAIL, send_at=None):
    header = SMTPAPIHeader()
    body = get_template(template_name).render(Context(context))
    if send_at:
        send_at = {"send_at": send_at}
        header.set_send_at(send_at)
    email = EmailMultiAlternatives(
        subject=subject,
        body=body,
        from_email=from_email,
        to=to,
        bcc=bcc,
        headers={'X-SMTPAPI': header.json_string()}

    )
    email.attach_alternative(body, 'text/html')
    email.send()

Don't forget to set it in header X-SMTPAPI cause I couldn't find it anywhere.. And send_at should be a timestamp

Also here you could see how to add headers or anything but with sendgrid.SendGridClient: https://sendgrid.com/docs/Utilities/code_workshop.html/scheduling_parameters.html

import sendgrid
...
sg = sendgrid.SendGridClient('apiKey')
message = sendgrid.Mail()
message.add_to('John Doe <example@mailinator.com>')
message.set_subject('Example')
message.set_html('Body')
message.set_text('Body')
message.set_from('Doe John <example@example.com>')
message.smtpapi.set_send_at(timestamp)
sg.send(message)