What do you do when your email server has been blacklisted and you are unable to send emails to certain domains? It’s best to be proactive and not get on the blacklists in the first place, but in the unfortunate event you do get blacklisted, here are some notes.
Checking Blacklists
First thing is we need to see which lists we are on. There are a couple of services that check multiple blacklists
Send an email to “abuse_rbl@abuse-att.net” with your Mail Server IP address, the domain and ask to be delisted. You should get an auto-reply and then they usually will do something about it in 24-48 hours
These are all fairly straight forward to check out. Some of them you will need to enter in an email, or maybe set up an account, others are as simple as requesting the IP to be delisted.
In this post, we will be using Node.JS and the nodemailer library to send email. We need to have an email account with an email provider to send email. Gmail or some other email provider should work.
Prerequisites
First lets install some tools
sudo apt install nodejs npm
Now lets install nodemailer
npm install nodemailer
Writing the Code to Send Email
Now that we have nodemailer installed, we can write or copy our code. Create a file called maill.js and make it look similar to the following.
// We can pass in the email text as an argument
const emailText = process.argv.slice(2);
// Or we can just have it as a variable
// const emailText = "NodeJS test email message."
console.log("args " + args)
const nodemailer = require("nodemailer");
const transporter = nodemailer.createTransport({
host: "mail.emailserver.com",
port: 465, // If your email server does not support TLS, change to 587
secure: true, // If you are using port 587, change to false. Upgrade later with STARTTLS
auth: {
user: "smtpuser@emailserver.com",
pass: "notpassword)",
},
});
const mailOptions = {
from: 'user@emailserver.com',
to: "touser@email.com",
subject: 'Test Email using NodeJS',
text: `${emailText}`
};
transporter.sendMail(mailOptions, function(error, info){
if (error) {
console.log(error);
} else {
console.log('Email sent: ' + info.response);
}
});
Update the following variables
host: to your host email server
user: to the email user that is sending email. It should have an account on the email server
pass: password for your email user that is sending the email
from: email address that is sending the email
to: email account(s) you are sending email to
subject: subject of your email
Now we can proceed to send email
Sending Email
We can now run the code by saving our file and running it directly with NodeJS
nodejs ./mail.js "This is the body text for the email"
Hit Return and look for the email. If something went wrong, it should throw an error.
You can change the emailText variable if you would rather have the message body inside the code.
Code Explanation and Notes
A little explanation on the code.
The second line “const emailText = process.argv.slice(2);” is used to pass in a command line argument to use as the text for the body of the email. You can delete the line and uncomment line 4 if you would rather use a variable inside the code.
Your email server should support using SSL/TLS on port 465. If it does not, you may need to use STARTTLS which uses port 587, and then set secure to false. STARTTLS should upgrade the connection to be encrypted. But it’s opportunistic. You can read more about STARTTLS, SSL/TLS here https://mailtrap.io/blog/starttls-ssl-tls/
You can change the “to: ” in the mailOptions object to an array of email addresses to send the email to multiple people at once.
to: ["email1@email.com", "email2@email.com", "etc"],
We’ll be using telnet to connect to a mail server and send ourselves an email.
The parts in bold are the commands to enter.
[bob@linux ~]$ telnet mail.website.com 25
Trying mail.website.com...
Connected to mail.website.com.
Escape character is '^]'.
220-mail.website.com ESMTP Exim 4.85 #2 Mon, 09 May 2022 22:12:59
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
HELO domainto.sendfrom.com
250 mail.website.com Hello domainto.sendfrom.com [192.168.1.2]
MAIL FROM: <bob@incredigeek.com>
250 OK
RCPT TO: <bob@incredigeek.com>
250 Accepted
DATA
354 Enter message, ending with "." on a line by itself
Subject: Test MessageThis is a test.
250 OK id=5a1g7i-1347MT-1p
QUIT
221 mail.website.com closing connection
Connection closed by foreign host.
That should be everything that you need. Send a test email to an external email account to verify that it works.
Note that it looks like sending an email locally to email addresses on the same domain or to yourself bypass the filter and do not get the disclaimer added.
The following links were helpful for getting this set up.
The first two “2, and 2,ab” mean that the message has not been read. The bottom 2 “2,S and s,Sab” mean that the message has been read or “seen?”. Guess that is what the S is for. Not sure what ab is for.
