Blog post illustration

Onboarding emails custom sequences with Mailgun

October 14, 2021 4 min read

For Typebot, I needed to send custom onboarding emails to my newly registered users. For example:

  • The user created an account but didn't create a typebot
  • The user created a typebot but didn't publish it
  • The user published a typebot but didn't embed it on a site

It also needed to be a sequence (of at least 3 emails) to maximize the chances the user comes back to the tool.

I tried to look for third-party tools but I figured that it would be complicated to handle different scenarios as I would need to update the user properties in the tools by calling an API each time a user has done an action?

So, I ultimately decided to use Mailgun and scheduled cloud functions (In my case, Firebase Cloud functions).

Mailgun is an API that "enable you to send, receive and track email effortlessly".

If you're a developer or a control freak, like me, you probably would prefer to code your own email sequence engine 😃.

Create the email templates in Mailgun

With Mailgun, you can create email templates that you can then call with their JS SDK. You can find the Templates page under the Sending tab.

Here is one of my templates:

<p>Your typebot’s looking good so far. 💎</p>
<p>Finished with editing? Then let&#39;s move on to the next step, shall we?</p>
  Once you’re finished with personalizing it, all you need to do is to
  <a href="{{chatbotId}}/share"
    >publish it and share it to your audience</a
  >. <br />Then you&#39;ll start collecting those precious responses to help
  grow your business.
<p>Let me know if you have any questions with publishing your typebot.</p>
{{{signature}}} {{{unsubscribe}}}

Then, to send an email using this template, you can directly set it in the mail options in your code:

export const sendOnboardingEmail = async ({
}: SendEmailProps) => {
  const mailOptions = {
    from: '"Baptiste Arnaud" <>',
    "h:List-Unsubscribe": `${userId}`,
    "h:Reply-To": '"Baptiste Arnaud" <>',
    "h:X-Mailgun-Variables": JSON.stringify({
      signature: htmlSignature,
      unsubscribe: htmlUnsubscribe(userId),
  if (sendDate) mailOptions["o:deliverytime"] = sendDate.toUTCString();

  await mg.messages.create("", mailOptions);

o:deliverytime option allows you to set a future send date to avoid sending the email right away. For example, you can decide to send it at the same time your user registered 3 days ago.

I've created a scheduled function that runs every day at 4am:

export const sendOnboardingEmails = functions
  .pubsub.schedule("0 4 * * *")
    sentryWrapper(async () => {
      await sendFirstOnboardingEmails(3);
      await sendSecondOnboardingEmails(6);
      await sendThirdOnboardingEmails(8);

Every function sends the corresponding email according to what the user has done.

Stop the sequence if a user replies

Imagine the user answers to the first onboarding email. Something like

Thank you for this email, I'll try out what you say in the next few days.

I didn't want to send him the next automated emails. So I had to call a webhook whenever someone replies to an email. Mailgun allows you to do this 🤯

It's located under the Receiving tab. You can forward emails to your API endpoint:

My route handler looks like this:

import { NextApiRequest, NextApiResponse } from "next";
import formidable from "formidable";

const form = formidable();

async function handler(req: NextApiRequest, res: NextApiResponse) {
  const data = await new Promise<{
    err: unknown;
    fields: formidable.Fields;
    files: formidable.Files;
  }>((resolve, reject) => {
    form.parse(req, (err, fields, files) => {
      if (err) reject({ err });
      resolve({ err, fields, files });
  const { From } = data.fields;
  const email = From.toString()
  if (!email) return;
  await updateUserOnboardingProp(email);
  return res.send({ message: `Sequence stopped successfuly for ${email}` });

It grabs the email and simply updates a user field in the database so that you won't send him another onboarding email.


That's it! It's still a basic implementation. But having full control (with code) over what you can send is a huge pro for me.

Let me know if you have any questions. You can reach out to me on Twitter @baptisteArno