Rabsztok · Nov 3, 2026 · Nov 3, 2026 · Nov 3, 2026 · Nov 3, 2026 · Nov 5, 2026
diff --git a/README.md b/README.md
@@ -115,7 +115,7 @@ Send emails to your Sandbox for testing purposes:
 ```ruby
 require 'mailtrap'
 
-client = Mailtrap::Client.new(api_key: 'your-api-key', sandbox: true, inbox_id: YOUR_INBOX_ID)
+client = Mailtrap::Client.new(api_key: 'your-api-key', sandbox: true, sandbox_id: YOUR_SANDBOX_ID)
 client.send(mail)
 
 # You can also pass the request parameters directly
@@ -139,9 +139,8 @@ Meaning your recipients will receive emails only in the default encoding which
 is `quoted-printable`, if you send with Mailtrap API.
 
 For those who need to use `7bit` or any other encoding, SMTP provides
-better flexibility in that regard. Go to your _Mailtrap account_ → _Email Sending_
-→ _Sending Domains_ → _Your domain_ → _SMTP/API Settings_ to find the SMTP
-configuration example.
+better flexibility in that regard. Go to your _Mailtrap account_ → _Domains_
+→ _Your domain_ → _Integration_ to find the SMTP configuration example.
 
 ### Multiple Mailtrap Clients
 
@@ -175,17 +174,17 @@ Email API:
 
 - Full Email Sending – [`full.rb`](examples/full.rb)
 - Batch Sending – [`batch.rb`](examples/batch.rb)
-- Sending Domains API – [`sending_domains_api.rb`](examples/sending_domains_api.rb)
+- Domains API – [`domains_api.rb`](examples/domains_api.rb)
 - Sending Stats API – [`stats_api.rb`](examples/stats_api.rb)
 - Email Logs API – [`email_logs_api.rb`](examples/email_logs_api.rb)
 - Webhooks API – [`webhooks_api.rb`](examples/webhooks_api.rb)
 - Suppressions API – [`suppressions_api.rb`](examples/suppressions_api.rb)
 - Tracking Opt-outs API – [`tracking_opt_outs_api.rb`](examples/tracking_opt_outs_api.rb)
 
-Email Sandbox (Testing):
+Email Sandbox:
 
 - Projects CRUD – [`projects_api.rb`](examples/projects_api.rb)
-- Inboxes CRUD - [`inboxes_api.rb`](examples/inboxes_api.rb)
+- Sandboxes CRUD - [`sandboxes_api.rb`](examples/sandboxes_api.rb)
 - Sandbox Messages CRUD - [`sandbox_messages_api.rb`](examples/sandbox_messages_api.rb)
 - Sandbox Attachments API - [`sandbox_attachments_api.rb`](examples/sandbox_attachments_api.rb)
 
@@ -218,6 +217,40 @@ General:
 - Action Mailer – [`action_mailer.rb`](examples/action_mailer.rb)
 - Verifying webhook signatures – [`webhooks_signature_verification.ru`](examples/webhooks_signature_verification.ru)
 
+## Renamed APIs
+
+Email Sandbox inboxes are now called sandboxes, and sending domains are now called
+domains. The old names still work and call the same API endpoints, but they print a
+deprecation warning and will be removed in a future major release.
+
+| Deprecated | Use instead |
+|------------|-------------|
+| `Mailtrap::InboxesAPI` | `Mailtrap::SandboxesAPI` |
+| `Mailtrap::Inbox` | `Mailtrap::Sandbox` |
+| `Mailtrap::SendingDomainsAPI` | `Mailtrap::DomainsAPI` |
+| `Mailtrap::SendingDomain` | `Mailtrap::Domain` |
+| `Mailtrap::Client.new(inbox_id:)` and the ActionMailer `inbox_id` setting | `sandbox_id` |
+| `#inbox_id` on `Client`, `SandboxMessagesAPI` and `SandboxAttachmentsAPI` | `#sandbox_id` |
+
+The other old names warn once per process. `Mailtrap::Inbox` and `Mailtrap::SendingDomain`
+use Ruby's `deprecate_constant`, so they warn only when Ruby's deprecation warnings are
+enabled (for example, `ruby -W:deprecated`), and they can warn more than once. Attributes and filters that
+mirror API fields keep their names, such as `SandboxMessage#inbox_id`, `Project#inboxes`
+and the `sending_domain_ids:` stats filter.
+
+The once-per-process warnings print whether or not Ruby's deprecation warnings are
+enabled, so `-W:no-deprecated` doesn't hide them. To silence them, filter out the
+warnings tagged `[mailtrap]`:
+
+```ruby
+module SilenceMailtrapDeprecations
+  def warn(message, ...)
+    super unless message.include?('[mailtrap]')
+  end
+end
+Warning.extend(SilenceMailtrapDeprecations)
+```
+
 ## Migration guide v1 → v2
 
 Change `Mailtrap::Sending::Client` to `Mailtrap::Client`.

diff --git a/bin/record-vcr b/bin/record-vcr
@@ -6,8 +6,8 @@
 #
 # Usage:
 #   bin/record-vcr                                              # all specs
-#   bin/record-vcr spec/mailtrap/sending_domains_api_spec.rb    # single file
-#   bin/record-vcr spec/mailtrap/sending_domains_api_spec.rb:42 # single example
+#   bin/record-vcr spec/mailtrap/domains_api_spec.rb            # single file
+#   bin/record-vcr spec/mailtrap/domains_api_spec.rb:42         # single example
 #   bin/record-vcr -e "#update"                                 # filter by name
 #   bin/record-vcr --org spec/mailtrap/sub_accounts_api_spec.rb # use organization API token
 #

diff --git a/examples/action_mailer.rb b/examples/action_mailer.rb
@@ -10,7 +10,7 @@
 #   # Switch to bulk sending (@see https://help.mailtrap.io/article/113-sending-streams)
 #   bulk: true,
 #   # Switch to sandbox sending (@see https://help.mailtrap.io/article/109-getting-started-with-mailtrap-email-testing)
-#   sandbox: true, inbox_id: 12,
+#   sandbox: true, sandbox_id: 12,
 # }
 
 # Now you can use ActionMailer to deliver mail through Mailtrap.

diff --git a/examples/batch.rb b/examples/batch.rb
@@ -10,7 +10,7 @@
 # Bulk sending (@see https://help.mailtrap.io/article/113-sending-streams)
 # client = Mailtrap::Client.new(bulk: true)
 # Sandbox sending (@see https://help.mailtrap.io/article/109-getting-started-with-mailtrap-email-testing)
-# client = Mailtrap::Client.new(sandbox: true, inbox_id: 12)
+# client = Mailtrap::Client.new(sandbox: true, sandbox_id: 12)
 
 # Batch sending with text and html content
 batch_base = Mailtrap::Mail.batch_base_from_content(

diff --git a/examples/company_info_api.rb b/examples/company_info_api.rb
@@ -1,13 +1,13 @@
 require 'mailtrap'
 
 account_id = 3229
-sending_domain_id = 1
+domain_id = 1
 client = Mailtrap::Client.new(api_key: 'your-api-key')
 company_info_api = Mailtrap::CompanyInfoAPI.new(account_id, client)
 
-# Create company info for a sending domain
+# Create company info for a domain
 company_info_api.create(
-  sending_domain_id,
+  domain_id,
   name: 'Mailtrap',
   address: '123 Main St',
   city: 'San Francisco',

diff --git a/examples/domains_api.rb b/examples/domains_api.rb
@@ -0,0 +1,36 @@
+require 'mailtrap'
+
+account_id = 3229
+client = Mailtrap::Client.new(api_key: 'your-api-key')
+domains = Mailtrap::DomainsAPI.new(account_id, client)
+
+# Create new domain
+domain = domains.create(domain_name: 'example.com')
+# => #<struct Mailtrap::Domain id=1, domain_name="example.com">
+
+# Get all domains
+domains.list
+# => [#<struct Mailtrap::Domain id=1, domain_name="example.com">]
+
+# Get domain
+domain = domains.get(domain.id)
+# => #<struct Mailtrap::Domain id=1, domain_name="example.com">
+
+# Update domain configuration
+domains.update(
+  domain.id,
+  open_tracking_enabled: true,
+  click_tracking_enabled: true,
+  tracking_opt_out_enabled: true,
+  auto_unsubscribe_link_enabled: false,
+  inbound_enabled: false
+)
+# => #<struct Mailtrap::Domain id=1, domain_name="example.com", ...>
+
+# Send setup email
+domains.send_setup_instructions(domain.id, email: 'jonathan@mail.com')
+# => nil
+
+# Delete domain
+domains.delete(domain.id)
+# => nil
diff --git a/examples/full.rb b/examples/full.rb
@@ -53,7 +53,7 @@
 # client = Mailtrap::Client.new(api_key: 'your-api-key', bulk: true)
 
 # Sandbox sending (@see https://help.mailtrap.io/article/109-getting-started-with-mailtrap-email-testing)
-# client = Mailtrap::Client.new(api_key: 'your-api-key', sandbox: true, inbox_id: 12)
+# client = Mailtrap::Client.new(api_key: 'your-api-key', sandbox: true, sandbox_id: 12)
 
 client.send(mail)
 

diff --git a/examples/inboxes_api.rb b/examples/inboxes_api.rb
diff --git a/examples/marketing_stats_api.rb b/examples/marketing_stats_api.rb
@@ -17,7 +17,7 @@
 #      unsubscription_count=12, unsubscription_rate=0.01,
 #      sent_count=1250>
 
-# Narrow to campaigns only (or automations only), for some sending domains and email service providers
+# Narrow to campaigns only (or automations only), for some domains and email service providers
 marketing_stats.get(
   start_date: today - 29,
   end_date: today,

diff --git a/examples/sandbox_attachments_api.rb b/examples/sandbox_attachments_api.rb
@@ -1,10 +1,10 @@
 require 'mailtrap'
 
 account_id = 3229
-inbox_id = 12
+sandbox_id = 12
 message_id = 123
 client = Mailtrap::Client.new(api_key: 'your-api-key')
-sandbox_attachments = Mailtrap::SandboxAttachmentsAPI.new(account_id, inbox_id, message_id, client)
+sandbox_attachments = Mailtrap::SandboxAttachmentsAPI.new(account_id, sandbox_id, message_id, client)
 
 # List all attachments for a sandbox message (up to 30)
 sandbox_attachments.list

diff --git a/examples/sandbox_messages_api.rb b/examples/sandbox_messages_api.rb
@@ -1,11 +1,11 @@
 require 'mailtrap'
 
 account_id = 3229
-inbox_id = 12
+sandbox_id = 12
 client = Mailtrap::Client.new(api_key: 'your-api-key')
-sandbox_messages = Mailtrap::SandboxMessagesAPI.new(account_id, inbox_id, client)
+sandbox_messages = Mailtrap::SandboxMessagesAPI.new(account_id, sandbox_id, client)
 
-# List all sandbox messages in the inbox (optional: search, page, last_id)
+# List all messages in the sandbox (optional: search, page, last_id)
 sandbox_messages.list
 # => [#<struct Mailtrap::SandboxMessage id=1, subject="Welcome", ...>]
 

diff --git a/examples/sandboxes_api.rb b/examples/sandboxes_api.rb
@@ -0,0 +1,39 @@
+require 'mailtrap'
+
+account_id = 3229
+client = Mailtrap::Client.new(api_key: 'your-api-key')
+sandboxes = Mailtrap::SandboxesAPI.new(account_id, client)
+
+# Create new sandbox
+sandbox = sandboxes.create(name: 'Test Sandbox', project_id: 123_456)
+# => #<struct Mailtrap::Sandbox id=1, name="Test Sandbox">
+
+# Get all sandboxes
+sandboxes.list
+# => [#<struct Mailtrap::Sandbox id=1, name="Test Sandbox">]
+
+# Update sandbox
+sandboxes.update(sandbox.id, name: 'Test Sandbox Updated')
+# => #<struct Mailtrap::Sandbox id=1, name="Test Sandbox Updated">
+
+# Get sandbox
+sandbox = sandboxes.get(sandbox.id)
+# => #<struct Mailtrap::Sandbox id=1, name="Test Sandbox Updated">
+
+# Delete all messages (emails) from the sandbox
+sandboxes.clean(sandbox.id)
+
+# Mark all messages in the sandbox as read
+sandboxes.mark_as_read(sandbox.id)
+
+# Reset SMTP credentials of the sandbox
+sandboxes.reset_credentials(sandbox.id)
+
+# Turn the email address of the sandbox on/off
+sandboxes.toggle_email_username(sandbox.id)
+
+# Reset username of email address per sandbox
+sandboxes.reset_email_username(sandbox.id)
+
+# Delete sandbox
+sandboxes.delete(sandbox.id)
diff --git a/examples/sending_domains_api.rb b/examples/sending_domains_api.rb
diff --git a/examples/tracking_opt_outs_api.rb b/examples/tracking_opt_outs_api.rb
@@ -37,7 +37,7 @@
   puts page.data.size
 end
 
-# Opt an email out of open and click tracking for a sending domain
+# Opt an email out of open and click tracking for a domain
 opt_out = tracking_opt_outs.create(email: 'tracked@example.com', domain_id: 12_345)
 # => #<struct Mailtrap::TrackingOptOut id="64d71bf3-1276-417b-86e1-8e66f138acfe", ...>
 

diff --git a/lib/mailtrap.rb b/lib/mailtrap.rb
@@ -22,10 +22,12 @@
 require_relative 'mailtrap/tracking_opt_outs_api'
 require_relative 'mailtrap/email_campaigns_api'
 require_relative 'mailtrap/marketing_stats_api'
+require_relative 'mailtrap/domains_api'
 require_relative 'mailtrap/sending_domains_api'
 require_relative 'mailtrap/company_info_api'
 require_relative 'mailtrap/email_logs_api'
 require_relative 'mailtrap/projects_api'
+require_relative 'mailtrap/sandboxes_api'
 require_relative 'mailtrap/inboxes_api'
 require_relative 'mailtrap/sandbox_messages_api'
 require_relative 'mailtrap/sandbox_attachments_api'

diff --git a/lib/mailtrap/account_accesses_api.rb b/lib/mailtrap/account_accesses_api.rb
@@ -9,9 +9,9 @@ class AccountAccessesAPI
 
     self.response_class = AccountAccess
 
-    # Retrieves a list of account accesses with optional filtering by domain, inbox, or project IDs
+    # Retrieves a list of account accesses with optional filtering by domain, sandbox, or project IDs
     # @param domain_ids [Array<Integer>] Optional array of domain IDs to filter by
-    # @param inbox_ids [Array<Integer>] Optional array of inbox IDs to filter by
+    # @param inbox_ids [Array<Integer>] Optional array of sandbox IDs to filter by
     # @param project_ids [Array<Integer>] Optional array of project IDs to filter by
     # @return [Array<AccountAccess>] List of account access objects
     # @!macro api_errors

diff --git a/lib/mailtrap/action_mailer/delivery_method.rb b/lib/mailtrap/action_mailer/delivery_method.rb
@@ -1,11 +1,13 @@
 # frozen_string_literal: true
 
+require_relative '../deprecation'
+
 module Mailtrap
   module ActionMailer
     class DeliveryMethod
       attr_accessor :settings
 
-      ALLOWED_PARAMS = %i[api_key api_host api_port bulk sandbox inbox_id].freeze
+      ALLOWED_PARAMS = %i[api_key api_host api_port bulk sandbox sandbox_id].freeze
 
       def initialize(settings)
         self.settings = settings
@@ -22,7 +24,16 @@ def deliver!(message)
       private
 
       def client
-        @client ||= Mailtrap::Client.new(**settings.slice(*ALLOWED_PARAMS))
+        @client ||= Mailtrap::Client.new(**client_settings)
+      end
+
+      def client_settings
+        params = settings.slice(*ALLOWED_PARAMS)
+        inbox_id = settings[:inbox_id]
+        return params if inbox_id.nil?
+
+        Deprecation.warn('The ActionMailer mailtrap_settings inbox_id', 'sandbox_id')
+        params.merge(sandbox_id: Deprecation.resolve_sandbox_id(params[:sandbox_id], inbox_id))
       end
     end
   end