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Before you can receive emails with Lettr, you need to configure an inbound domain and set up MX records to route incoming mail to Lettr’s servers.

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Prerequisites

Before setting up email receiving, ensure you have:
  • A verified Lettr account
  • Access to your domain’s DNS settings
  • A webhook endpoint ready to receive inbound email events (recommended)

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Step-by-Step Setup

1

Add an Inbound Domain

Navigate to Domains → Inbound in your dashboard and click Add Domain. Enter the domain or subdomain you want to use for receiving emails.
2

Configure MX Records

Add the provided MX records to your domain’s DNS settings. These records tell email servers to route mail to Lettr.
3

Verify MX Records

Click Verify in the dashboard to confirm your MX records are properly configured.
4

Set Up Webhooks

Configure a webhook endpoint to receive notifications when emails arrive.

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Adding an Inbound Domain

  1. Go to Domains → Inbound
  2. Click Add Domain
  3. Enter your domain (e.g., mail.example.com)
  4. Click Create
The dashboard will display the MX records you need to add, along with the domain’s current status (unverified until DNS is configured).
Inbound domain management is available through the Lettr dashboard. There is no public API endpoint for creating or managing inbound domains.

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DNS Configuration

Add these MX records to your domain’s DNS settings:
TypeHost/NamePriorityValue
MX@ or subdomain10rx1.sparkpostmail.com
MX@ or subdomain10rx2.sparkpostmail.com
MX@ or subdomain10rx3.sparkpostmail.com
If you’re using a subdomain like mail.example.com, set the Host/Name field to mail instead of @.

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Understanding MX Priority

All three MX records use the same priority (10), which provides load balancing:
PriorityServerPurpose
10rx1.sparkpostmail.comMail server
10rx2.sparkpostmail.comMail server
10rx3.sparkpostmail.comMail server
With equal priority, sending servers distribute email across all three servers. If one is unavailable, the others handle delivery automatically.

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Verifying Your Domain

After adding MX records, verify they’re properly configured:
  1. Go to Domains → Inbound
  2. Find your domain and click Verify
  3. Wait for the verification to complete
Once verified, the domain’s status changes from unverified to valid, confirming your MX records are correctly configured.

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Domain Status

StatusDescription
validAll MX records found and configured correctly
unverifiedMX records not yet detected or incomplete

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Using Subdomains vs Root Domain

We recommend using a subdomain for inbound email:
ConfigurationUse Case
mail.example.comGeneral inbound processing
reply.example.comReply tracking for transactional emails
support.example.comCustomer support emails
inbound.example.comWebhook-triggered workflows
Using subdomains lets you keep your root domain’s MX records pointing to your regular email provider (Gmail, Microsoft 365, etc.) while routing specific addresses through Lettr.

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DNS Propagation

DNS changes can take time to propagate:
Typical TimeDescription
5 minutesMost DNS providers
1-4 hoursSome registrars
Up to 48 hoursWorst case
If verification fails immediately after adding records, wait 15-30 minutes and try again. Use a tool like MXToolbox to check your MX records externally.

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Next Steps

Webhooks

Receive notifications when emails arrive

Routing

Route emails to different handlers

Attachments

Handle incoming attachments

Inbound Domains

Learn more about domain configuration