Note, this article is a technical article aimed at software developers. Some basic programming is required to receive and process posts from our API. This integration can often be done in just a couple of hours.

Popular online marketplaces such as Craigslist, Airbnb and many others as well as many online communities need to allow their market participants to communicate with each other without sharing their private data. Elastic Email provides a simple out of the box integration to enable anonymized email relaying functionality via our Inbound Email API.

Use example of the anonymous, two-way email communication

Let’s say you’re creating a new online marketplace, a classified site called where people can post their bicycles for sale. Members of this site sign up, take a picture and post their bike online.  Our example seller signs up with his email address from

Meanwhile, buyers browse the site looking for their perfect bike. When they find it, they want to send an email to the seller. The site wants to support this communication between participants but the participants' private email addresses should not be shared. 

When the buyer submits an email to the seller they, the seller, should receive the email from an anonymous branded address like: 

We want to allow them to reply to this email directly from their email inbox. When they do, the email should be sent directly to the buyer's actual email address from: 

The two can then have a “normal” email exchange between them without actually sharing their true personal email addresses. 

Optionally, the site should have the ability to monitor or sensor this communication and store the conversation in a thread on so the two participants could come back and review the conversation later. Airbnb does this, Craigslist does not. 

Anonymous email relying how to

How to set anonymized email relaying up using Elastic Email

Elastic Email makes setting up this two-way anonymous communication fast and easy using our inbound email API and a smart webhook. 

Step 1 - Setup DNS MX Record:

First, we must set up the mail received by our domain to arrive at Elastic Email’s inbound SMTP API. Since our example company has its actual email addresses at we can use a subdomain at to facilitate our buyer and sellers email. 

New MX record: MX points to

More detail on this setup step can be found here:

Once this is set up, then any email sent to will arrive at the Elastic Email inbound SMTP API and will be parsed. 

In addition to the MX record, you should also set up email security DNS records for SPF and DKIM for as outlined here:

Step 2 - Create a Webhook Endpoint:

Setup an HTTP webhook URL on your web server which can access the sellers and buyers who are stored in your app's database.  For our example, we will set up a new webhook endpoint at:

Once we have this URL we can add this to the inbound setup in our Elastic Email account. This completes the basic setup at Elastic Email. Now, any email that is sent to will be received by our SMTP API, parsed using our powerful MIME parsers and split into handy chunks of data which will be sent via HTTP POST to your web server.  

Step 3 - Use the Elastic Email outbound API to get the conversation started

Let’s say the buyer has just requested more information from the seller on one of the bikes. They entered their email in the app, wrote their message and hit send. 

When this happens stores the email address of the buyer as a new “buyer” account and assigns the buyer a unique ID. 

They then send an email to the sellers real email address containing the buyers message via the standard Elastic Email outbound API:

The critical step is to build the FROM email address of the message using the buyers unique ID - for example: 

The seller will receive the email and the buyer is protected from sharing their information.  

Step 4 - Receiving the reply via the Webhook:

When the seller replies to the email from their email software the message will be sent to the buyer's address @ We set up the MX server for that to go to Elastic Email’s inbound SMTP API. So it will be parsed and sent via HTTP to our webhook.   

When Elastic Email posts the inbound mail to your webhook, it will include quite a lot of data (all fields can be found here: For the sake of this example, we will focus on several specific fields:

from_email (from address)

to_list (list of email addresses the email was sent to separated by commas)

subject (email subject)

body_html (HTML body content)

body_html_reply (new content in the email only - this excludes historical thread information)

Each of these fields from the email that was received will be standard HTTP Post parameters. 

When receives this POST it must resolve the from_email and the to_list to the appropriate members on the site and then it can respond to the web request with instructions for Elastic Email on what to do with the email. 

The web response needs to look like this for Elastic Email to understand it:

{ relay_to: “buyers real email address”, from_email: “” } 

So the webhook must take the to_list of email addresses which in our example will be just one email address: - parse out the unique buyer ID and look up in the database the real email address for the buyer. 

It must also take the seller's real email address which is passed in via the from_email parameter and look up the seller's account to get their unique ID and build a private email address for them. In this case These two values are passed back to Elastic Email in the response format above as the response to the webhook call. 

Step 5 - Elastic Email does the rest

At this point, we’ve instructed Elastic Email to relay the email and resolved the private email addresses to use in the conversation. Elastic Email will now construct and submit a new outbound email back to the buyer using the seller's email address. The buyer can reply and the conversation can continue just as any normal email communication thread.  

how to set 2-way anonymous messaging

Bonus Step - storing messages in an inbox(Optional) 

If wanted to capture the conversation going on between the buyer and the seller and store it in an inbox in the app they can use the body_html_reply parameter to capture just the reply content added in each email (without the additional re: thread content that usually exists in email) and store this in their database so the participants could review the conversation later in the app.  

Easy to implement and widely needed feature

Using Elastic Email with a single webhook API call and a few DNS settings, we can set up a powerful, private and anonymous two-way email communication system between market or community participants. Enjoy! 
As always the Elastic Email support team is here to help if you have any questions getting your integration setup.

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