Send Emails from Your SAP CAP Application Using Nodemailer

Introduction

In this tutorial we integrate Nodemailer with SAP CAP for sending emails. To test this, we run smtp4dev in a docker container.

Prerequisites

Ensure you have a development environment set up for CAP, described here, as well as Docker, described here.

SMTP4Dev Setup

Start pulling and running smtp4dev using the following

docker run -d -p 5000:80 -p 2525:25 --name smtp4dev rnwood/smtp4dev

To verify this is running and working, run the following to view the smtp4dev logs:

docker logs -f smtp4dev

Then, in another terminal, run the following:

#!/bin/bash
SMTP_HOST=”localhost”
SMTP_PORT=2525
SENDER=”sender@127.0.0.1”
RECIPIENT=”recipient@127.0.0.1”
TIMESTAMP=$(date +%Y%m%d%H%M%S%N)
TIMESTAMP=$(date +%Y%m%d%H%M%S%N|cut -c 1-16)
echo $TIMESTAMP
curl --url “smtp://$SMTP_HOST:$SMTP_PORT” \
     --crlf \
     --mail-from “$SENDER” \
     --mail-rcpt “$RECIPIENT” \
     --upload-file - <<EOF
From: “Sender” <sender@example.com>
To: “Recipient” <recipient@example.com>
Subject: $TIMESTAMP

$TIMESTAMP
EOF

You should get some log lines as follows:

[INF] SMTP session started. ClientAddress: ::ffff:172.17.0.1
[INF] SMTP authentication successful - any credentials allowed. ClientAddress: ::ffff:172.17.0.1
[INF] SMTP authentication successful - any credentials allowed. ClientAddress: ::ffff:172.17.0.1
[INF] SMTP message received. ClientAddress: ::ffff:172.17.0.1, From: noreply@yourcompany.com, To: customer@example.
com, SecureConnection: false, DeclaredSize: null
[INF] Processing received message for mailbox ‘Default’ for recipients ‘[”customer@example.com”]’
[INF] Message processing completed. MessageId: “de0b284a-f956-4a05-8e9c-7b8b1136d75b”, Mailbox: Default, ImapUid: 9
00
[INF] SMTP session completed. ClientAddress: ::ffff:172.17.0.1, MessageCount: 1, Duration: 59.5304ms

Alternatively, try out the web interface at

http://localhost:5000

The smpt4dev Web Interface

CAP Project Setup

Create a new CAP project and install dependencies:

# Create project
cds init email-integration
cd email-integration
npm install nodemailer
npm install dotenv --save-dev

We will use nodemailer for sending emails and use dotenv for managing environment variables.

Configure Environment Variables

Create a .env file in your project root and set up the following environment variables based on your smtp4dev configuration:

SMTP_HOST=127.0.0.1
SMTP_PORT=2525
SMTP_USER=”dummy”
SMTP_PASS=”1234”
SMTP_SECURE=false
SMTP_TLS_REJECTUNAUTHORIZED=false

Ensure the SMTP values match up with your smtp4dev container. Add .env to your .gitignore if you plan on committing:

echo “.env” >> .gitignore

To actually use the above settings, create a ./srv/server.js file in your project root to load the environment variables from the .env file:

// Load environment variables from .env file
require(’dotenv’).config();
const cds = require(’@sap/cds’);
cds.once(’bootstrap’, app => {
});
module.exports = cds.server;

Define the Data Model

Next we will define the data model in db/schema.cds:

namespace com.email;
entity Email {
  key ID:UUID;
      ![from]:String;
      to:String;
      subject:String;
      html:String;
}

The scenario above is a very simple test schema. Note that we use ![from] instead of from because this is a reserved keyword.

Define the Service

Create srv/email-service.cds:

using{com.email as db}from’../db/schema’;
service EmailService{
 entity Email as projection on db.Email;
}

Create Email Service Module

Create srv/email-service.js:

const cds=require(’@sap/cds’);
const nodemailer=require(’nodemailer’);
module.exports=async(srv)=>{
 const{Email}=srv.entities;
 const transportOptions={
  host:process.env.SMTP_HOST,
  port:process.env.SMTP_PORT,
  auth:{
   user:process.env.SMTP_USER,
   pass:process.env.SMTP_PASS
  },
  secure:process.env.SMTP_SECURE===true,
  tls:{
   rejectUnauthorized:process.env.SMTP_TLS_REJECTUNAUTHORIZED===true
  }
 };
 const transporter=nodemailer.createTransport(transportOptions);
 srv.after(’CREATE’,Email,async(email,req)=>{
  const mailOptions={
   from:email.from,
   to:email.to,
   subject:email.subject,
   html:email.html
  };
  try{
   await transporter.sendMail(mailOptions);
   console.log(`Email sent for email ${email.ID}`);
  }catch(error){
   console.error(`Failed to send email: ${error.message}`);
  }
 });
};

Deploy and Test

Now you can deploy the database with cds deployand run the server using npm run start .

You can send emails by creating an Email entity as follows:

#!/bin/bash
curl -X POST “http://localhost:4004/odata/v4/email/Email” \
     -H “Content-Type: application/json” \
     -d ‘{
           “from”: “from@example.com”,
           “to”: “to@example.com”,
           “subject”: “subject”,
           “html”: “test”
         }’

You can verify this by checking out the smtp4dev web interface. The sent Emails will be persisted in the database, and you can inspect them using the following:

#!/bin/bash
curl “http://localhost:4004/odata/v4/email/Email”

References

• smpt4dev

• SAP CAP Documentation

• Nodemailer Documentation