Sending emails through Mailgun using Codeigniter (and using Mailgun campaigns)

As a developer and startup founder, I occasionally find myself looking at web apps and thinking either “This is too expensive” or “This doesn’t do exactly what I want.” My solution (for better or worse) is to build what I want myself. And when I’m building a quick app that I’m going to be the primary user of, my framework of choice is Codeigniter. It’s fast to develop in. It’s easy. And, most importantly, it’s stable (so I don’t have to worry about keeping up-to-date with weekly version releases… I’m looking at you, Node.JS).

The past few days I’ve been working on an emailing app. After all, why use something as simple and beautiful as Mailchimp when you can build your own clunky, ugly, Frankenstein version, right?

Anyway, a friend suggested Mailgun, and the free 10,000 emails a month sounded like a good deal, so I figured I’d leave SendGrid behind for a few days.

Overall, I’m unbelievably pleased with Mailgun. It’s a solid system. I might even switch RocketBolt to it. However, troubleshooting it with Codeigniter was a bit more tricky than I’m used to. Turns out not too many people are talking about how to make Mailgun and Codeigniter play nicely together. It’s not difficult. It’s just more difficult than it should be because no one has posted instructions. So I thought I’d give a quick write-up. Future spammers of the world… you’re welcome!

Integrating Mailgun into Codeigniter:

The best way to hook Mailgun into Codeigniter is by using Mailgun’s SMTP integration. Start by creating an email.php file in your application’s “config” folder (if you don’t already have one). In the body, you can paste something like this:

<?php if (!defined('BASEPATH')) exit('No direct script access allowed');

  $config['mailtype'] = 'html';
  $config['charset'] = 'utf-8';

  $config['protocol'] = 'smtp';
  $config['smtp_host'] = 'ssl://';
  $config['smtp_port'] = 465;
  $config['smtp_user'] = '[your Mailgun SMTP username]';
  $config['smtp_pass'] = '[your Mailgun SMTP password]';
  $config['smtp_timeout'] = '4';
  $config['crlf'] = '\n';
  $config['newline'] = '\r\n';

Here’s a little note to future me: the “$config[‘crlf’]” line is needed to fix a Codeigniter bug that prevents subject lines from being more than 75 characters. (Hey… I said Codeigniter is quick, but I didn’t say it was perfect.)

Once you’ve done that, you’re good to go. Send emails through Codeigniter as normal, and you’ll be burning through those 10,000 free Mailgun emails in no time!

Creating Mailgun campaigns with Codeigniter:

This turned out to be a bit more tricky. Mailgun has a slick campaign tracking system. But, in order to use it, you need to add a custom email header. Turns out Codeigniter doesn’t have a pre-built way of doing that, so you’ll need to extend CI’s email class. As I mentioned at the beginning of this post, the Interwebs are a bit lacking for direct answers about sending campaign headers for Mailgun, but I was able to adapt the solution from an answer about how to do a similar thing for Sendgrid. Here’s what you need to know:

Step 1:

Create a file in your application’s “libraries” folder called “MY_Email.php” and then add the following code:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

  class MY_Email extends CI_Email {

      public function __construct($config = array())
          if (count($config) > 0)
              $this->_smtp_auth = ($this->smtp_user == '' AND $this->smtp_pass == '') ? FALSE : TRUE;
              $this->_safe_mode = ((boolean)@ini_get("safe_mode") === FALSE) ? FALSE : TRUE;

          log_message('debug', "Email Class Initialized");

      // this will allow us to add headers whenever we need them
      public function set_header($header, $value)
          $this->_headers[$header] = $value;

Step 2:

Once you’ve done that, adding a Mailgun campaign header is as simple as including the following line of code when you first start constructing your email:

  $this->email->set_header('X-Mailgun-Campaign-Id', [Your Mailgun Campaign ID]);

And that’s it. Just make sure to include that line before setting anything else in the email (for example… if you want an HTML email and are loading a View), otherwise it’ll throw a pleasant “headers already sent” error.

That’s it for today. By the way… how’d you like my first coding tutorial? Not nearly as fun as everything else I write, huh? I also learned that my original theme was terrible for showing code, but I think I’ve finally fixed that. Lucky you!


I teach in Duke University’s Innovation & Entrepreneurship program and founded RocketBolt. I write about startups, pedagogy, entrepreneurship, engineering, and poetry. They’re all related, I promise.

Leave a Reply

Your email address will not be published. Required fields are marked *


  • Walked into the @dukeinnovation Bullpen and was excited to find @kdhoch. I hear #dukeinsiliconvalley was fantastic, but I'm glad to have him back in #durham. Though, after five weeks on the Left Coast, I was kind of hoping he'd have frosted tips. #ohwell #entrepreneurlife
  • 4th of July celebratory steak dance #happy4th #steak #babycarnivore
  • Catching a summer lecture by my favorite @dukeuniversity undergrad professor, Dr. George Gopen. 12 years later, he's still showing 400-person auditoriums how the #grammar rules they learned in grade school hurt their #professionalwriting. Lesson #1: "Context controls meaning." #rhetoric #memorylane
  • Ended the morning with the right amount of fingers and toes. My yard ended the morning with one less tree. #yardwork #homeownership #imissrenting
  • Puppy birthday ice cream! Happy 7th birthday to my favorite ball of fur. #furbaby #puppy #doggyicecream
  • Shook off 2+ decades of rust to build a block masterpiece today. Looking forward to #fathersday 2021 when Adeline is old enough for us to break out the real @lego sets 😊
  • Love when my @dukeinnovation graduates want to Skype to discuss a post-Duke #startup. 
Hopefully they're all competing to be my first student to produce a unicorn. 
Don't let me down @jordanmartinez15 🤞 
#entrepreneurship #hustle #duke2017
  • Only thing better than a geeky discussion about #sales pipelines with @adwerxre VP of Sales @cleithe is doing it over drinks on top of the @thedurhamhotel #saleslife #entrepreneurlife #playinghooky #durham
  • While updating an investor today I used the phrase "shopping for unicorn saddles." When we tried to figure out what that actually meant, here's what we came up with. Any better ideas? #entrepreneurship #startups #venturecapital #unicornsaddle🦄
  • Tate caught a rainbow while moving into our new house. Is that a good omen, or were the former owners of my house Care Bears? #lucky #potofgold #notinkansasanymore
  • Carference Call (n): A video conference that takes place in your car because you booked meetings too close together. #entrepreneurship #startups #hustling #randomparkinglot
  • Finally getting to use my fancy new parking permit in my fancy new parking lot thanks to @kdhoch -- my personal parking guru 😉 #toolazytowalk

Follow Me!