json2smtp

An email proxy: input: json, output: smtp call

For a legacy project I needed to have a proxy that reads json input and execute a smtp call in order to send emails. So I created a small proxy for emails in go (golang)

Read more about why I needed it here: https://www.c2kb.com/json2smtp

NEW: If you want to use an online service of json to smtp: https://www.json2smtp.net

Table of Contents

1. How it works
2. The json struct object
   1. Simple object
   2. Full with smtp data
      1. Adding attachments
3. How to install
   1. Build and compile
   2. Execute the proxy examples
      1. Run the proxy
      2. Run in the background
      3. Simple execute
   3. Recommended architecture
4. Download binaries
5. Todo
6. Libraries used
7. Thank you

How it works:

Simple calling diagram

The json struct object

Simple object:

curl -X POST \
 -H "Content-Type: application/json" \
 -d '{
"from": "john doe <john@example.com>",
"to": ["kermit@muppets.com", "oneperson@example.com"],
"cc": ["email1@example.com"],
"bcc": ["secret@example.com"],
"subject": "email subject line",
"message": "message body in text/html to be sent",
"attachments": {"filename.pdf": "base64 file encoded", "anotherfilename.txt": "base64 file encoded"},
 }' \
 http://localhost:8080/

Full with smtp data:

curl -X POST \
 -H "Content-Type: application/json" \
 -d '{
"from": "john doe <john@example.com>",
"to": ["kermit@muppets.com", "oneperson@example.com"],
"cc": ["email1@example.com"],
"bcc": ["secret@example.com"],
"subject": "email subject line",
"message": "message body in text/html to be sent",
"attachments": {"filename.pdf": "base64 file encoded", "anotherfilename.txt": "base64 file encoded"},
"smtphost": "smtp.example.com - optional parameter",
"smtpport": 587 - optional paramater,
"smtpuser": "username - optional parameter",
"smtppassword": "password - optional parameter"
 }' \
 http://localhost:8080/

Attachments

In order to send attachments with your json email struct you need to construct an object of base64 encoded string of your binary file.

How to install:

Download the code and run it

git clone https://github.com/caviv/json2smtp.git
go run ./
go run ./ --help

Build and compile

Download the code compile it and run with help command

git clone https://github.com/caviv/json2smtp.git
go build ./
./json2smtp --help

Execute the proxy examples

Command line help:

json2smtp utility https://www.c2kb.com/json2smtp v1.0.1 2023-11-13
Get json input and calls smtp - function as a json to smtp proxy
Options:
  -port int
    	the port to listen on (default 8080)
  -smtphost string
    	smtp host, e.g. smtp.example.com
  -smtpoverride
    	true - allows to pass smtp parameters in the json call, false will always use the config smtp data (default true)
  -smtppassword string
    	password for the smtp user
  -smtpport int
    	the port to listen on (default 587)
  -smtpuser string
    	username for the smtp

Run the proxy:

json2smtp --port=8200 --smtphost='smtp.example.com' --smtpport=587 --smtpuser='username' --smtppassword='password' --smtpoverride=false

Run in the background:

nohup json2smtp --port=8200 --smtphost='smtp.example.com' --smtpport=587 --smtpuser='username' --smtppassword='password' >> logfile.log 2>&1 &

Simple execute:

In this way the calling client will have to pass the smtp server details in each call because we don't set the smtp default server for the proxy. The default port to listen on is 8080.

json2smtp 

Recommended architecture

Download binaries:

https://www.c2kb.com/json2smtp

Todo:

• Replace the mail.v2 package to a newer one - as recommended here: https://www.reddit.com/r/golang/comments/17w2l9s/comment/k9fve4r/
• Create delayed sending of emails / asynchronic sending - I think that could be useful
• Allow sending of plain/html and plain/text body in emails

( Look at the issues of this project: https://github.com/caviv/json2smtp/issues )

Libraries used

This external libraries are used in the project:

require gopkg.in/mail.v2 v2.3.1 require gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0

Thank you

contact me on support at c2kb.com