Custom domains
Use a custom domain to receive mail at addresses that you control. An inbound route receives mail for every recipient on its configured domain.
Use a dedicated subdomain, such as replies.example.com, if your main domain uses another mail provider. An MX record directs mail for the configured domain to Lettermint.
Choose an exact or wildcard domain
| Choose | Matching behavior |
|---|---|
| Exact domain | Receive mail for one domain, such as replies.example.com. |
| Wildcard domain | Receive mail for subdomains below one domain, such as *.replies.example.com. |
An exact domain matches only the configured domain:
support@replies.example.commatchesreplies.example.com.support@eu.replies.example.comdoes not matchreplies.example.com.
A wildcard domain matches one or more subdomains below the configured domain:
support@eu.replies.example.commatches*.replies.example.com.support@vip.eu.replies.example.comalso matches*.replies.example.com.support@replies.example.comdoes not match*.replies.example.com.
The last address uses the base domain. Configure the exact domain on a separate route if you must receive it.
If more than one custom domain matches, Lettermint uses this order:
- An exact custom domain.
- The most specific wildcard domain.
For example, *.eu.example.com receives mail for customer.eu.example.com instead of *.example.com.
Configure the domain
Add the catch-all domain
- Open the inbound route and select Settings.
- Find Use your own domain.
- Enter the domain in Catch-all domain.
- Select Save changes.
Enter an exact domain such as replies.example.com. For a wildcard domain, enter *.replies.example.com.
You can use a wildcard only at the left side of the domain.
If another person manages your DNS, select Share instructions after you save the domain. Enter their email address. Lettermint sends a link that shows the required MX record and its priority. The link is valid for seven days.
Add the MX record
Create this record with your DNS provider:
| Field | Value |
|---|---|
| Type | MX |
| Host | replies.example.com |
| Priority | 10 |
| Value | lettermint.mx |
For a wildcard route, use the wildcard domain as the record name. For example, use *.replies.example.com.
DNS providers use different formats for record names. Some require only the host. Other providers require the complete domain.
Do not add https:// or an IP address to the MX value.
Verify the MX record
Return to the route Settings page. Select Verify.
Lettermint marks the domain as verified when it finds the expected MX record.
Send a test message
Send an email to any address on the verified domain. For example, send to support@replies.example.com.
Open the webhook delivery log. Confirm that your endpoint received message.inbound.
Route recipients with plus addressing
Custom domains preserve plus tags in the webhook payload. Use a plus tag to route messages without creating additional inbound routes.
For a message sent to support+order-4821@replies.example.com:
Code
recipient contains the SMTP envelope recipient. subaddress contains the text after +, without the plus sign.
Generated @inbound.lettermint.co addresses do not support plus addressing. They must match the generated address exactly.
Existing MX records that point to inbound.lettermint.co continue to work. You do not need to change them.
Troubleshooting
Why does MX verification fail?
- Confirm that the MX value is
lettermint.mxor the compatibleinbound.lettermint.covalue. - Confirm that the record name matches Catch-all domain.
- Include
*.in the record name for a wildcard domain. - Check that your DNS provider did not add the domain name twice.
- Wait for DNS caches to update. Then select Verify again.
- Check the record with
dig MX replies.example.comor a similar DNS tool.
Why does the wildcard not receive mail for the base domain?
This behavior is expected. *.replies.example.com matches tenant.replies.example.com. It does not match the base domain replies.example.com.
Add the exact domain to another inbound route if you must receive mail for the base domain.
Why is mail going to another provider?
Check all MX records for the receiving domain. Records for multiple providers can send mail to a different provider.
Use a dedicated subdomain to keep inbound routes separate from employee mail and other mailboxes.
Why did a broader wildcard route receive the message?
Check the configured domains. Lettermint selects the most specific matching wildcard domain.
For example, *.eu.example.com takes precedence over *.example.com. An exact domain always takes precedence over a wildcard domain.