Send attached file with Mailgun using python

Question

I'm trying to send an email with an attached file with the Mailgun API using requests.post.

In their documentation they alert that you must use multipart/form-data encoding when sending attachments, I'm trying this:

import requests
MAILGUN_URL = 'https://api.mailgun.net/v3/sandbox4f...'
MAILGUN_KEY = 'key-f16f497...'


def mailgun(file_url):
    """Send an email using MailGun"""

    f = open(file_url, 'rb')

    r = requests.post(
        MAILGUN_URL,
        auth=("api", MAILGUN_KEY),
        data={
            "subject": "My subject",
            "from": "my_email@gmail.com",
            "to": "to_you@gmail.com",
            "text": "The text",
            "html": "The<br>html",
            "attachment": f
        },
        headers={'Content-type': 'multipart/form-data;'},
    )

    f.close()

    return r


mailgun("/tmp/my-file.xlsx")

I've defined the header to be sure that the content type is multipart/form-data, but when I run the code, I get a 400 status with reason: Bad Request

What's wrong? I need be sure that i'm using multipart/form-data and I'm using correctly the attachment parameter

I would advise to go over this [documentation](https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html) before doing anything on the web. If you know the error codes you immediately know where to look for the bugs. In this case: some parameter is missing or is warded incorrectly — limbo, Jun 20 '16 at 21:13

score 23 · Accepted Answer · edited Feb 04 '23 at 02:06

You need to use the files keyword argument. Here is the documentation in requests.

And an example from the Mailgun documentation:

def send_complex_message():
    return requests.post(
        "https://api.mailgun.net/v3/YOUR_DOMAIN_NAME/messages",
        auth=("api", "YOUR_API_KEY"),
        files=[("attachment", open("files/test.jpg")),
               ("attachment", open("files/test.txt"))],
        data={"from": "Excited User <YOU@YOUR_DOMAIN_NAME>",
              "to": "foo@example.com",
              "cc": "baz@example.com",
              "bcc": "bar@example.com",
              "subject": "Hello",
              "text": "Testing some Mailgun awesomness!",
              "html": "<html>HTML version of the body</html>"})

So modify your POST to:

r = requests.post(
    MAILGUN_URL,
    auth=("api", MAILGUN_KEY),
    files = [("attachment", f)],
    data={
        "subject": "My subject",
        "from": "my_email@gmail.com",
        "to": "to_you@gmail.com",
        "text": "The text",
        "html": "The<br>html"
    },
)

This should work fine for you.

Works for me but only if I don't specify the `headers` arg. Seems this is handled automatically anyway. — Jans Rautenbach, Aug 07 '20 at 14:07

Send attached file with Mailgun using python

1 Answers1