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POST
/
send
/
batch
Send multiple emails in a batch
curl --request POST \
  --url https://api.lettermint.co/v1/send/batch \
  --header 'Content-Type: application/json' \
  --header 'x-lettermint-token: <api-key>' \
  --data '
[
  {
    "from": "<string>",
    "to": [
      "<string>"
    ],
    "subject": "<string>",
    "route": "<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"
    },
    "tag": "welcome-email",
    "html": "<string>",
    "text": "<string>",
    "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
​
to
string[]
required
​
subject
string
required
Maximum string length: 998
​
route
string
​
cc
string[]
​
bcc
string[]
​
reply_to
string[]
​
headers
string[]

Custom headers to include in the email.

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

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

Example:
{
  "user_id": "123",
  "campaign_id": "welcome-2025"
}
​
tag
string | null

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

Example:

"welcome-email"

​
html
string | null
Minimum string length: 3
​
text
string | null
Minimum string length: 3
​
attachments
object[]

Response

Emails 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