Send

Send an email

POST

https://api.lettermint.co/v1

/send

Send an email › Headers

x-lettermint-token

string

Idempotency-Key

string

Send an email › Request Body

SendMailRequest

from

string · required

subject

string · maxLength: 998 · required

to

string[] · minItems: 1 · required

route

string

tag

string | null

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

html

string | null · minLength: 3

text

string | null · minLength: 3

cc

string[]

bcc

string[]

reply_to

string[]

object

Custom headers to include in the email.

object

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

settings

object | null

Per-email settings that override the selected route settings for this email only.

object[]

Send an email › Responses

message_id

string · required

status

MessageStatus · enum · required

Enum values:

pending

queued

suppressed

processed

delivered

opened

clicked

soft_bounced

POST/send

curl --request POST \
  --url https://api.lettermint.co/v1/send \
  --header 'Content-Type: application/json' \
  --data '
{
  "route": "route",
  "from": "from",
  "subject": "subject",
  "tag": "welcome-email",
  "html": "html",
  "text": "text",
  "to": [
    "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"
  },
  "settings": {
    "track_opens": false,
    "track_clicks": true
  },
  "attachments": [
    {
      "filename": "filename",
      "content": "content",
      "content_type": "application/pdf",
      "content_id": "logo-image"
    }
  ]
}
'

Example Request Body

{
  "route": "route",
  "from": "from",
  "subject": "subject",
  "tag": "welcome-email",
  "html": "html",
  "text": "text",
  "to": [
    "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"
  },
  "settings": {
    "track_opens": false,
    "track_clicks": true
  },
  "attachments": [
    {
      "filename": "filename",
      "content": "content",
      "content_type": "application/pdf",
      "content_id": "logo-image"
    }
  ]
}

json

Example Responses

{
  "message_id": "message_id",
  "status": "pending"
}

json

application/json

Send multiple emails in a batch

POST

https://api.lettermint.co/v1

/send/batch

Send up to 500 emails in a single request. Each email in the batch supports the same parameters as the single send endpoint.

Send multiple emails in a batch › Headers

x-lettermint-token

string

Idempotency-Key

string

Send multiple emails in a batch › Request Body

object[] · minItems: 1

from

string · required

to

string[] · minItems: 1 · required

subject

string · maxLength: 998 · required

route

string

cc

string[]

bcc

string[]

reply_to

string[]

headers

string[]

Custom headers to include in the email.

metadata

string[]

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

tag

string | null

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

settings

object | null

Per-email settings that override the selected route settings for this email only.

html

string | null · minLength: 3

text

string | null · minLength: 3

object[]

Send multiple emails in a batch › Responses

Array of message IDs and their status

object[]

message_id

string · required

status

MessageStatus · enum · required

Enum values:

pending

queued

suppressed

processed

delivered

opened

clicked

soft_bounced

POST/send/batch

curl --request POST \
  --url https://api.lettermint.co/v1/send/batch \
  --header 'Content-Type: application/json' \
  --data '
[
  {
    "route": "route",
    "from": "from",
    "to": [
      "string"
    ],
    "cc": [
      "string"
    ],
    "bcc": [
      "string"
    ],
    "reply_to": [
      "string"
    ],
    "subject": "subject",
    "headers": {
      "X-Custom-Header": "custom-value",
      "X-Campaign-ID": "12345"
    },
    "metadata": {
      "user_id": "123",
      "campaign_id": "welcome-2025"
    },
    "tag": "welcome-email",
    "settings": {
      "track_opens": false,
      "track_clicks": true
    },
    "html": "html",
    "text": "text",
    "attachments": [
      {
        "filename": "filename",
        "content": "content",
        "content_type": "application/pdf",
        "content_id": "logo-image"
      }
    ]
  }
]
'

Example Request Body

[
  {
    "route": "route",
    "from": "from",
    "to": [
      "string"
    ],
    "cc": [
      "string"
    ],
    "bcc": [
      "string"
    ],
    "reply_to": [
      "string"
    ],
    "subject": "subject",
    "headers": {
      "X-Custom-Header": "custom-value",
      "X-Campaign-ID": "12345"
    },
    "metadata": {
      "user_id": "123",
      "campaign_id": "welcome-2025"
    },
    "tag": "welcome-email",
    "settings": {
      "track_opens": false,
      "track_clicks": true
    },
    "html": "html",
    "text": "text",
    "attachments": [
      {
        "filename": "filename",
        "content": "content",
        "content_type": "application/pdf",
        "content_id": "logo-image"
      }
    ]
  }
]

json

Example Responses

[
  {
    "message_id": "message_id",
    "status": "pending"
  }
]

json

application/json

Generic

Send an email

POST

https://api.lettermint.co/v1

/send

Send an email › Headers

x-lettermint-token

string

Idempotency-Key

string

Send an email › Request Body

SendMailRequest

from

string · required

subject

string · maxLength: 998 · required

to

string[] · minItems: 1 · required

route

string

tag

string | null

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

html

string | null · minLength: 3

text

string | null · minLength: 3

cc

string[]

bcc

string[]

reply_to

string[]

object

Custom headers to include in the email.

object

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

settings

object | null

Per-email settings that override the selected route settings for this email only.

object[]

Send an email › Responses

message_id

string · required

status

MessageStatus · enum · required

Enum values:

pending

queued

suppressed

processed

delivered

opened

clicked

soft_bounced

Send multiple emails in a batch

POST

https://api.lettermint.co/v1

/send/batch

Send up to 500 emails in a single request. Each email in the batch supports the same parameters as the single send endpoint.

Send multiple emails in a batch › Headers

x-lettermint-token

string

Idempotency-Key

string

Send multiple emails in a batch › Request Body

object[] · minItems: 1

from

string · required

to

string[] · minItems: 1 · required

subject

string · maxLength: 998 · required

route

string

cc

string[]

bcc

string[]

reply_to

string[]

headers

string[]

Custom headers to include in the email.

metadata

string[]

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

tag

string | null

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

settings

object | null

Per-email settings that override the selected route settings for this email only.

html

string | null · minLength: 3

text

string | null · minLength: 3

object[]

Send multiple emails in a batch › Responses

Array of message IDs and their status

object[]

message_id

string · required

status

MessageStatus · enum · required

Enum values:

pending

queued

suppressed

processed

delivered

opened

clicked

soft_bounced