Create email with Gmail API - shell

Question

I'm testing Gmail API here https://developers.google.com/gmail/api/reference/rest/v1/users.drafts/create but is it possible to create a full email with sender, subject, body and load a gmail template and send it through curl command?
This is what I tried but I am getting an empty message:

Answer 1

How to send an email based on a draft with the Gmail API
This is one approach you could take:
Using users.draft list
{
"drafts": [
{
"id": "r-1561xxx",
"message": {
"id": "179891xxx",
"threadId": "179891xxx"
}
}
],
"resultSizeEstimate": 1
}
Then users.draft get with one of the id in the previous request:
You can retrieve the current MIME message contained in the draft by calling drafts.get with the parameter format=raw.
(The data is sanitized)
{
"id": "r-1561xxx",
"message": {
"id": "179891xxx",
"threadId": "179891xxx",
"labelIds": [
"DRAFT"
],
"snippet": "Name: Reason: Company:",
"sizeEstimate": 635,
"raw": "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",
"historyId": "67xxx",
"internalDate": "1628xxx"
}
}
The raw attribute is where the message is. It's encoded in base64. Decoded it looks like this:
MIME-Version: 1.0
Date: Fri, 13 Aug 2021 16:12:09 +0200
Message-ID: <CAFdukbnrdxQxxxx#mail.gmail.com>
Subject: draft1
From: Sender <sample#gmail.com>
To: Receiver <sample#gmail.com>
Content-Type: multipart/alternative; boundary="000000000000eb4b5805c9716fd2"
--000000000000eb4b5805c9716fd2
Content-Type: text/plain; charset="UTF-8"
Name:
Reason:
Company:
--000000000000eb4b5805c9716fd2
Content-Type: text/html; charset="UTF-8"
<div dir="ltr">Name:<div><br></div><div>Reason:</div><div><br></div><div>Company:</div></div>
--000000000000eb4b5805c9716fd2--
Sending
In the guide it says:
Create the email content in some convenient way and encode it as a base64url string.
Create a new message resource and set its raw property to the base64url string you just created.
The text should conform to the rfc2822.
So make a plain text email like this (some field you can omit, like date and message ID):
MIME-Version: 1.0
Subject: draft1
From: Sender <sample#gmail.com>
To: Receiver <sample#gmail.com>
Content-Type: multipart/alternative; boundary="000000000000eb4b5805c9716fd2"
--000000000000eb4b5805c9716fd2
Content-Type: text/plain; charset="UTF-8"
Name: TooNetCreation
Reason: TooNetCreation
Company: TooNetCreation
--000000000000eb4b5805c9716fd2
Content-Type: text/html; charset="UTF-8"
<div dir="ltr">Name: TooNetCreation<div><br></div><div>Reason: TooNetCreation</div><div><br></div><div>Company: TooNetCreation</div></div>
--000000000000eb4b5805c9716fd2--
Which encodes to:
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
Which you can send with:
curl --request POST \
'https://gmail.googleapis.com/gmail/v1/users/me/messages/send?key=[YOUR_API_KEY]' \
--header 'Authorization: Bearer [YOUR_ACCESS_TOKEN]' \
--header 'Accept: application/json' \
--header 'Content-Type: application/json' \
--data '{"raw":"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"}' \
--compressed
After which it should return an instance of the message and you will have send an email!
References
users.draft list
users.draft get
users.messages send
Sending email guide
Working with drafts guide