What is inbound email routing and how to set it up (with examples)

Amy Elliott Amy Elliott
· 9 min read · Tips and resources · July 14th, 2023
Inbound email routing is a cool feature that enables users of your app to interact with it via email. Let’s take a look at how inbound routing works and the steps to set it up.

The ability to send emails to customers and users is essential for any company that does business online. There is a lesser-known feature, however, that allows you to optimize that communication and improve the user experience of your app or website.

Inbound email routing, or inbound email processing, allows MailerSend to receive emails on your behalf and parse them to your app.

There are a few different use cases for inbound routing, which makes it a versatile feature that you can use to customize your email setup. But before we get into that, let’s take a look at how it works.

Want to skip right to the part on how to configure inbound routing? Jump forward to the steps.

How inbound email processing works

Inbound email processing involves creating routes, or pipelines, to process incoming email messages in various ways. When an inbound email is received by your Email Service Provider (ESP), it will process and parse the message as defined by the inbound email route.

The end result could be as simple as forwarding the email to a specified email address or integrating the message into your app. Or, more complex inbound routes might trigger an event via a webhook or allow users to protect their personal details and communicate anonymously with anonymized email relaying.

Inbound email routing use cases and examples

Inbound email processing is a reliable and efficient way to direct incoming messages to the correct recipient. But it can also be used for a lot more than that. Here’s how.

1. Post and reply to comments and messages

When a user receives a message or comment in your app, you can trigger a transactional email message notification to be delivered to their inbox. Inbound routing allows users to respond to messages and comments by replying to the email.

When an email reply is sent, the ESP will receive, process and parse the email message so that it will be displayed within your app interface as a message or comment reply.

Here’s a good example of this in use from the vacation rental app, Airbnb. Airbnb lets users and hosts message each other within the app but recipients can also respond to messages by simply replying to the message notification email that gets delivered to their inbox.

Example of an email message that can be replied to and uses inbound routing from Airbnb.

If you click reply to this email from your inbox, you’ll notice the email address is unlike regular email addresses.

Example of an auto-generated email address for inbound routing.

This is because the email address has been generated by Airbnb to receive and process incoming messages so that they can be parsed to the app’s messaging interface.

An example of an inbound message parsed to an app from Airbnb.

If you’d like to integrate this type of functionality into your app, check out our guide on enabling the use of email replies to post comments or messages.

2. Customer support ticketing

This use case builds on the ability to reply to messages via email reply and adds some extra functionality to make customer support requests more efficient. When a customer submits a request—by either contact form or email—the message can be forwarded to a specific department based on rules. For example, when a message is sent to a specific domain or subdomain, the message can be forwarded to the relevant person or department.

The conversation can then be continued through email replies, which can be processed and parsed into the app interface and/or the customer support team’s helpdesk software.

In MailerSend, remember to use the X-MailerSend-MessageID header to enable email threads, so that each email reply will be added to the same email thread in the customer’s inbox. This will prevent their inbox from filling up with tons of emails and keep ongoing replies to conversations grouped together.

Here’s an example of inbound email routing used for customer support ticketing from Help Scout.

When the user or agent replies via email, the email will also appear in the Help Scout interface.

Help Scout email parsed to the app.

Organizing your customer support messaging in this way with inbound routing allows your support agents and customers to keep all communication organized, without manual intervention. Replies can be quickly sent via email and automatically organized in the Help Scout app.

It also allows team members to collaborate on solving issues. When communication is limited to inboxes, only the inbox owners can view the conversation. But when email replies are parsed to the app, the whole team can view them and contribute.

3. In-app chat

As well as allowing replies via email, you can also use inbound email processing to facilitate anonymized in-app messaging and chat, for example, in gaming. When a user wants to send a message to another user, they’ll select the user, which is identified by the ESP from their email address. All personal information, including the email address, is anonymized so that the sent message is received, processed and parsed by the ESP to be forwarded to the recipient within the app.

4. Process email content/attachments

Inbound routing can also be used to simplify tasks, such as processing and storing email content and attachments. This could be as simple as automatically moving attachments to an online storage account or more complex, for example, processing content and parsing it to the app.

An awesome example of this functionality in action can be found in the travel planning and itinerary app, Wanderlog.

Example of inbound routing for content processing from Wanderlog.

When you click Forward email you’re given an auto-generated email address to forward your confirmation to.

Wanderlog inbound forwarding email address.

Once your email has been forwarded to the address given, the ESP processes it and sends the message to the webhook URL to be added to the app.

Email content parsed to the Wanderlog app.

Add list items

Another similar use case would be using inbound email routing to add items to a list. Apps that allow users to create lists, for example, shopping lists or to-do lists, can allow users to add items to the list via email.

To-do list app, Todoist, is a great example of an app that allows users to send or forward emails to create tasks. It generates a unique email address for each project.

Todoist app with the ability to email tasks to a project.

It even allows you to set due dates, add labels and set priorities by adding the information to the subject line or email body.

Example of an email sent to Todoist to create a task.

The email is sent and then the content is parsed to the app to create a new task.

Task details parsed to the Todoist app from the email.

Create posts

If you've ever found yourself needing to post a blog post or article but without access to your laptop, inbound routing could be the ideal solution. You can configure an inbound route to process email content and display it as a post on your website. A good example of this is WordPress' Post by Email function.

It allows you to generate a unique email address and then create posts in any email client—including mobile. The subject is used as the title and the body of the email the content.

Benefits of inbound email routing

As you can see from the use cases and examples above, inbound routing allows you to build a more advanced and efficient email system and provide additional functionality for your service or app. As a result, it can help you to:

1. Save time and resources. Inbound email processing can be used to automatically route messages to specific departments or people. This ensures that important incoming messages are instantly delivered to the most appropriate recipient, without manual sorting and forwarding.

2. Optimize workflows and improve customer communication. Since inbound routing automatically routes messages, it speeds up response times. This allows customer service teams to provide support to users faster as well as increase their productivity.

3. Allow users to engage in 2-way conversations. By parsing incoming messages to your app, users are able to reply to messages and comments via email which will then seamlessly appear in your app interface.

4. Maintain privacy for users and employees. Anonymized email relaying allows users to communicate with each other and with team members while keeping their personal details private. What’s more, you can keep personal or important business email addresses hidden by using public-facing emails (think, for example) and then routing incoming messages to the appropriate person or department.

5. Make your email more flexible and scalable. As a business grows and departments and personnel change, inbound routing makes it easy to adapt to new team structures and policies. You can simply make a few small changes to your inbound routes to keep incoming messages running as usual.

How to implement inbound routing with MailerSend

You can set up multiple inbound routes for each domain you have in your account. Getting started is simple:

1. Go to the Domains page and click Manage for the domain you want to create an inbound route for.

2. In the Inbound route section, click Add an inbound route.

3. Enter a Name to be used to identify the inbound route. Below this, you’ll find your unique inbound email address for this route. This is the email address you want emails to be sent to so that they can be processed and parsed by MailerSend before being forwarded.

If you’d like to use your own domain name for the inbound email address, you can enable Inbound domain forwarding. This will allow you to enter a custom subdomain.

Note: If you choose to use a custom subdomain, you’ll need to add an MX record to your DNS with the value matching your custom inbound email address. You can find out more information about this, as well as inbound domain forwarding catch filters and priorities in our Inbound routing guide.

4. In the Filter emails section, you’ll select which emails to accept based on the email address of incoming emails. Learn more about the different filters available.

5. Finally, in the Route to section, add the email address/es or endpoint/s you’d like to route inbound mail to.

For parsing email content to your app, you’ll also need to create an API token and set up a webhook URL in your app that can receive JSON payloads and respond with a 500 error status or 200 OK status.

Learn how to set up the posting of comments with email replies.

Create an inbound route via API

To create a new inbound route use the following POST request:


The request body will look something like this, where under the forwards parameter, type will equal ‘webhook’ and value will equal your webhook URL. 

   "name":"Test name",

For more information on how to get, update and delete inbound routes, check out our API reference.

Note: The maximum email size for inbound emails is 50MB. File attachments have a limit up to 10MB, which counts towards the total email size.

Make email more efficient with inbound routing

Inbound routing is an impressive tool. While simple email forwarding is its most basic use, there are tons of possibilities when it comes to optimizing your transactional email and customer communication, and advancing your app functionality.

If you’d like to try inbound email processing and explore its capabilities, give MailerSend a go. Our friendly support team is available to answer any questions and help you get started!

Are you using inbound routing? Let us know in the comments about your use case and we might feature it!

Amy Elliott
I’m Amy, Content Writer at MailerSend. As a child, I dreamt about writing a book and practiced by tearing pages from an A4 notepad and binding them with sugar paper. The book is pending but in the meantime, I love taking a deep dive into technical topics and sharing insights on email metrics and deliverability.