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POST
/
send
Send an email
curl --request POST \
  --url https://api.lettermint.co/v1/send \
  --header 'Content-Type: application/json' \
  --header 'x-lettermint-token: <api-key>' \
  --data '
{
  "from": "<string>",
  "subject": "<string>",
  "to": [
    "<string>"
  ],
  "route": "<string>",
  "tag": "\"welcome-email\", \"Welcome_Email\", \"Order Confirmation 2024\"",
  "html": "<string>",
  "text": "<string>",
  "cc": [
    "<string>"
  ],
  "bcc": [
    "<string>"
  ],
  "reply_to": [
    "<string>"
  ],
  "headers": {
    "X-Custom-Header": "custom-value",
    "X-Campaign-ID": "12345"
  },
  "metadata": {
    "user_id": "123",
    "campaign_id": "welcome-2025"
  },
  "attachments": [
    {
      "filename": "<string>",
      "content": "<string>",
      "content_id": "<string>"
    }
  ]
}
'
{
  "message_id": "<string>",
  "status": "pending"
}

Authorizations

​
x-lettermint-token
string
header
required

Project-specific Sending API token. Find this in your project settings.

Headers

​
x-lettermint-token
string
required

Your project's Sending API token

​
Idempotency-Key
string

Optional idempotency key to prevent duplicate sends

Body

application/json
​
from
string
required
​
subject
string
required
Maximum string length: 998
​
to
string[]
required
​
route
string
​
tag
string | null

Tag to categorize and filter emails (alphanumeric, underscores, hyphens, spaces allowed).

Example:

"\"welcome-email\", \"Welcome_Email\", \"Order Confirmation 2024\""

​
html
string | null
Minimum string length: 3
​
text
string | null
Minimum string length: 3
​
cc
string[]
​
bcc
string[]
​
reply_to
string[]
​
headers
object

Custom headers to include in the email.

Example:
{
  "X-Custom-Header": "custom-value",
  "X-Campaign-ID": "12345"
}
​
metadata
object

Metadata to track with the email (not added as email headers).

Example:
{
  "user_id": "123",
  "campaign_id": "welcome-2025"
}
​
attachments
object[]

Response

Email accepted for delivery

​
message_id
string
required
​
status
enum<string>
required
Available options:
pending,
queued,
suppressed,
processed,
delivered,
soft_bounced,
hard_bounced,
spam_complaint,
failed,
blocked,
policy_rejected,
unsubscribed