Nodemailer with Docker

Question

I am trying to send multiple emails from a docker container working through register365.

This is the code used

export class Emailer { transporter: nodemailer.Transporter; constructor() { this.transporter = nodemailer.createTransport(smtpTransport({ host: 'smtp.reg365.net', auth: { user: 'myuser', pass: mypassword' } })); } public async sendEmail(to,body) { try { return await this.transporter.sendMail({to,from: '"TEST" < [e-mail] >',text: body, subject: ' WE NEED THE CONTENT AND DESIGN OF THIS EMAIL!!!!'}); } catch(error) { console.log('Email error'); console.dir(error); } } } 

This works fine if I run express with npm, but if I run it with docker, it will fail with this error Error: Connection closed

It only fails using smtp.reg.356.net, if I use Gmail it will work fine

This is the docker file that I am using

 FROM node:8 RUN mkdir -p /usr/src/app WORKDIR /usr/src/app RUN npm install -g nodemon COPY package.json /usr/src/app/ RUN npm install COPY ./dist /usr/src/app/dist EXPOSE 3005 EXPOSE 25 CMD [ "npm", "start" ] 

Many thanks.

EDIT: As required, running telnet smtp.reg365.net 25 returns this telnet: could not resolve smtp.reg.356.net/25: Name or service not known

Output from cat / etc / resolv.conf on the host machine

 domain Hitronhub.home nameserver 89.101.160.5 nameserver 89.101.160.4 

In a docker container

 search hitronhub.home nameserver 127.0.0.11 options ndots:0 

Answer 1

Create the file /etc/docker/daemon.json

 { "dns": ["89.101.160.5", "89.101.160.4"] } 

Restart the docker service and try again and see if this works for you.

You may be on an office network that has its own DNS servers that you should use. Therefore, you need to tell the Docker daemon which DNS server should use its containers. This is what creates the problem. The daemon.json file can be used to change the configuration of the daemon.