Sparkpost sending email using bash, CURL and SMTP protocol

I am trying to set up auto sending emails.

I figured out how to do it via HTTP:

curl -v \
-H "Content-Type: application/json" \
-H "Authorization: <MY_KEY>" \
-POST https://api.sparkpost.com/api/v1/transmissions \
-d '{
        "options":
        {
            "open_tracking": true,
            "click_tracking": true
        },
        "recipients":
        [
            {
                "address":
                {
                    "email": "to@domain.com"
                }
            }
        ],
        "content":
        {
            "from":
            {
                "name": "ME",
                "email": "from@domain.com"
            },
            "subject": "testing",
            "text": "testing"
        }
    }'

But i want to use SMTP protocol, because it's better way for me to generate emails with encoded in base64 files.

For example how i send mail to google account from bash script:

curl \
--ssl-reqd \
--url 'smtps://smtp.gmail.com:465' \
--user "$SENDER:$PASSWORD" \
--mail-from "$SENDER" \
--mail-rcpt "$RECIPIENT" \
-T "mail.txt" -k --anyauth

mail.txt contains:

From: "ME" <from@gmail.com>
To: "YOU" <to@gmail.com>
Subject: Test
Content-Type: multipart/mixed; boundary=MixedBoundary

--MixedBoundary\n
Content-Type: text/html; charset=\"utf-8
<html>
 <body><div>
  <p>Hello from linux terminal</p>
 </div></body>
</html>

--MixedBoundary
Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet; charset=utf-8
Content-Transfer-Encoding: base64
Content-Disposition: inline; filename=file.xlsx

...base64symbols...

[base64-encoded text]

--MixedBoundary-

The second option is much more convenient than the first, because i can easily collect any files that i need with bash script, so i want to remake it for sparkpost.

Unfortunately, I did not find a normal description for doing this literally. In the early stages, I ran into an authorization problem. As i understood from smtp api documentation: https://developers.sparkpost.com/api/smtp/ i have to authorize like:

my_email@domain.com:<MY_AUTH_KEY>

So i tried to connect to see output from sparkpost:

curl -v \
--ssl-reqd \
--url "smtps://smtp.sparkpostmail.com:587" \
--user "my_email@domain.com:<MY_AUTH_KEY>"

Output:

*   Trying 52.34.121.1:587...
* TCP_NODELAY set
* Connected to smtp.sparkpostmail.com (52.34.121.1) port 587 (#0)
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: /etc/ssl/certs
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* error:1408F10B:SSL routines:ssl3_get_record:wrong version number
* Closing connection 0
curl: (35) error:1408F10B:SSL routines:ssl3_get_record:wrong version number

So i have two questions:

How to get auth to sparkpost using SMTP?

Will the second option of sending emails work for sparkpost?

Solution

I figured out the problem more precisely and found errors. At first i tried to connect like this:

--url "smtps://smtp.sparkpostmail.com:587"

when I had to do it like this :

--url "smtp://smtp.sparkpostmail.com:587"

To get authorization in Sparkpost via SMTP according to the documentation instead of login you should write SMTP_Injection.

The authorization itself looks like this:

--user "SMTP_Injection:<YOUR_COOL_API_KEY>"

In general, everything looks like this:

curl -v \
--ssl --url "smtp://smtp.sparkpostmail.com:587" \
--user "SMTP_Injection:<YOUR_COOL_API_KEY>" \
--mail-from "from@domain.com" \
--mail-rcpt "to@domain.com" \
-T "example_file.txt" -k --anyauth

example_file.txt:

From: Name Surname <from@domain.com>
To: Name Surname <to@domain.com>
Subject: Example
Cc:
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="DELIMETER"

--DELIMETER
Content-Type: text/plain; charset=utf-8

Hello, Johny, look at this cat!

--DELIMETER
Content-Type: image/jpeg
Content-Transfer-Encoding: base64
Content-Disposition: inline; filename=funny_cat.jpg

LOMmL91PLmHcp0/E+eErv5zObgIRo/+vJJN6cto1cDRJ2g

--DELIMETER--