> ## Documentation Index > Fetch the complete documentation index at: https://developers.kit.com/llms.txt > Use this file to discover all available pages before exploring further. # Update a sequence email > Updates any field on a sequence email — `subject`, `preview_text`, `content`, `delay_value`, `delay_unit`, `send_days`, `position`, `email_template_id`, or `published`. Only fields included in the request body change; everything else is preserved. **Note:** pass `send_days: null` to revert a per-email schedule override and inherit the parent sequence's `send_days` again. The response will then return all 7 days, indicating no per-email restriction. **Warning:** sending `send_days` on an email with `delay_unit: "hours"` returns `422` — `send_days` only applies to day-based emails. **Warning:** changing `position` while subscribers are actively progressing through the sequence can cause emails to be sent out of order or skipped. The same caution applies to flipping `published` on a `position: 0` email — it triggers Kit to process all queued subscribers for that email. For the sequence-email model and how `delay_unit` and `send_days` interact, see [Create a sequence email](/api-reference/sequence-emails/create-a-sequence-email). ## OpenAPI ````yaml /api-reference/v4.json put /v4/sequences/{sequence_id}/emails/{id} openapi: 3.0.3 info: title: Kit API version: '4.0' servers: - url: https://api.kit.com security: [] paths: /v4/sequences/{sequence_id}/emails/{id}: put: tags: - Sequence Emails summary: Update a sequence email description: >- Updates any field on a sequence email — `subject`, `preview_text`, `content`, `delay_value`, `delay_unit`, `send_days`, `position`, `email_template_id`, or `published`. Only fields included in the request body change; everything else is preserved. **Note:** pass `send_days: null` to revert a per-email schedule override and inherit the parent sequence's `send_days` again. The response will then return all 7 days, indicating no per-email restriction. **Warning:** sending `send_days` on an email with `delay_unit: "hours"` returns `422` — `send_days` only applies to day-based emails. **Warning:** changing `position` while subscribers are actively progressing through the sequence can cause emails to be sent out of order or skipped. The same caution applies to flipping `published` on a `position: 0` email — it triggers Kit to process all queued subscribers for that email. For the sequence-email model and how `delay_unit` and `send_days` interact, see [Create a sequence email](/api-reference/sequence-emails/create-a-sequence-email). parameters: - name: id in: path required: true schema: type: integer example: 67 - name: sequence_id in: path required: true schema: type: integer example: 188 requestBody: content: application/json: schema: type: object properties: subject: type: string description: New subject line for the email preview_text: type: string nullable: true description: >- New preview text shown in email clients before the email is opened content: type: string nullable: true description: New HTML body content of the email delay_value: type: integer description: New delay value delay_unit: type: string enum: - days - hours description: >- New delay unit. Use `days` for schedule-aware delivery, `hours` for a fixed hourly delay email_template_id: type: integer nullable: true description: >- New email template ID for layout and styling. Pass `null` to clear published: type: boolean description: >- Pass `true` to publish a draft email or `false` to unpublish it send_days: type: array nullable: true items: type: string description: >- Days of the week this email may be sent. Pass a subset to restrict delivery, or `null` to reset to all days (inherits the sequence schedule) position: type: integer nullable: true description: New zero-based position of the email in the sequence example: subject: Updated subject preview_text: Updated preview content: null delay_value: 3 delay_unit: days email_template_id: null published: true send_days: - monday - wednesday - friday position: null responses: '200': description: Updates the sequence email and returns its details content: application/json: schema: type: object properties: email: type: object properties: id: type: integer sequence_id: type: integer subject: type: string preview_text: type: string email_address: type: string email_template_id: nullable: true published: type: boolean position: nullable: true delay_value: type: integer delay_unit: type: string send_days: type: array items: type: string content: type: string nullable: true required: - id - sequence_id - subject - preview_text - email_address - email_template_id - published - position - delay_value - delay_unit - send_days - content required: - email example: email: id: 66 sequence_id: 187 subject: Updated subject preview_text: Updated preview email_address: joe2536@ck.lol email_template_id: null published: true position: null delay_value: 3 delay_unit: days send_days: - monday - wednesday - friday content: Content 37 '401': description: Returns a 401 if the token and/or account cannot be authenticated content: application/json: schema: type: object properties: errors: type: array items: type: string required: - errors example: errors: - The access token is invalid '404': description: Returns a 404 when the provided id does not exist content: application/json: schema: type: object properties: errors: type: array items: type: string required: - errors example: errors: - Not Found '422': description: >- Returns a 422 with an error message when one or more of the parameters were invalid content: application/json: schema: type: object properties: errors: type: array items: type: string required: - errors example: errors: - 'delay_unit must be one of: days, hours' security: - API Key: [] - OAuth2: [] components: securitySchemes: API Key: description: Authenticate API requests via an API Key type: apiKey in: header name: X-Kit-Api-Key OAuth2: description: Authenticate API requests via an OAuth token type: oauth2 flows: authorizationCode: authorizationUrl: https://api.kit.com/v4/oauth/authorize tokenUrl: https://api.kit.com/v4/oauth/token refreshUrl: https://api.kit.com/v4/oauth/token scopes: read: Read access to Kit API v4 write: Write access to Kit API v4 ````