At Inboxroad, ensuring accurate email deliverability tracking is crucial. This document clarifies how we handle bounce events (both synchronous and asynchronous) and provides clear guidelines for configuring MX records to manage these bounces effectively
Understanding Bounce Types
When an email cannot be delivered, a bounce event is generated. There are two primary types of bounces:
Synchronous Bounce (B):
A bounce that happens during the initial SMTP conversation with the recipient’s server. The delivery fails immediately, and our server receives a bounce code.
Asynchronous / Remote Bounce (RB):
A bounce that occurs after the message was initially accepted by the recipient’s server. This often happens when a mailbox is full, a forwarding rule fails, or a content filter later rejects the message. The receiving server generates a Delivery Status Notification (DSN) and sends it back to the address specified in the `Return-Path`.
They are categorized as either Hard or Soft based on the nature of the failure, and both are used to suppress invalid addresses.
How Inboxroad Processes Bounces
Our system processes all bounces and immediately classifies them by their underlying cause to manage your recipient list health effectively. This classification determines the action we take for each email address.
- Hard Bounces: These indicate a permanent reason for failure, such as an invalid, non-existent, or disabled email address.
- Soft Bounces: These signal a temporary delivery issue, such as a full mailbox, a down recipient server, or a message that is too large.
Unmatched bounces or non-bounce messages sent to these MX records are discarded. We do not relay or forward other incoming mail.
MX Setup Options for Clients
To receive asynchronous bounces, you must configure your domain’s MX record. We offer two clear, consistent options:
Option 1: Dedicated Bounce Subdomain
This method isolates bounce handling without interfering with your regular inbound email.
How to set it up:
You can use a dedicated subdomain if needed, typically `rp.yourdomain.com`.
You create an MX record for this subdomain only, pointing to our PMTA server.
All DSNs (async bounces) for your campaigns will be sent to this subdomain, which routes them directly to our bounce processor.
Benefit:
Your root domain’s MX records remain untouched, ensuring your normal business email (e.g., Gmail, Microsoft 365) continues to function without interruption. However this is used only with integrations to Ongage and Mailwizz
Option 2: Root Domain MX
This method points your primary domain’s MX record to our servers.
How it works: You set the MX record for `yourdomain.com` to our PMTA server.
Consequence: This routes all inbound email for `yourdomain.com` to our servers. While our system will process DSNs, any other email (like personal or customer emails) will be discarded, as we do not operate a general-purpose mail server.
The Return-Path Header and Your Configuration
The `Return-Path` (also known as the envelope `MAIL FROM`) is the address to which asynchronous bounces are sent. However as mentioned above if you want to receive any email on this domain it has to be registered as subdomain on our webpage
Our System Behavior:
Our PMTA configuration uses the envelope `MAIL FROM` for bounce handling. We ensure this is set correctly for all outgoing mail.
Client Configuration:
In some interfaces (e.g., Ongage), there is an additional parameter that you may see a field to configure a bounce address. This is to ensure the `Return-Path` is set to an address at a domain for which you have configured the MX record. This step is not redundant; it is essential for ensuring DSNs can be routed back to our servers for processing.
The specifics of our partnership with Ongage is that every domain has `rp.` before domain name.
Troubleshooting and Common Questions
Why aren’t my Remote Bounces (RB) showing up in the dashboard?
Check your MX record: The most common cause is an incorrect or missing MX record for the domain used in your Return-Path. Verify that the MX record for your bounce domain (e.g.,rp.yourdomain.com) points correctly to our PMTA servers. You can also download log files through your dashboard, which states bounces in a detailed manner.
What happens to non-bounce emails sent to my MX record that points to Inboxroad?
As mentioned above, our servers are configured to process only DSNs (bounce messages). Any other email sent to an MX record pointing to our PMTA servers (e.g., a regular person emailing you) will be discarded and not delivered.
Summary of Best Practices
- Verify MX Records: After configuration, use an online MX lookup tool to confirm your subdomain’s MX record points to our servers.
- Ensure `Return-Path` Alignment: Configure your sending systems to use a `Return-Path` address from the domain for which you have set up the MX record.
- Monitor Both Bounce Types: Rely on our updated dashboard and systems that now account for all bounce types for accurate deliverability reporting.+
- Use a Dedicated Bounce Subdomain: `rp.subdomain` setup if you want to avoid disrupting your primary email flow.
For further assistance with your MX setup or bounce handling, please contact our support team.
