diff --git a/homeassistant/components/mailbox/__init__.py b/homeassistant/components/mailbox/__init__.py
index 3d482971ac9..1a5100123a5 100644
--- a/homeassistant/components/mailbox/__init__.py
+++ b/homeassistant/components/mailbox/__init__.py
@@ -1,4 +1,6 @@
 """Support for Voice mailboxes."""
+from __future__ import annotations
+
 import asyncio
 from contextlib import suppress
 from datetime import timedelta
@@ -10,11 +12,12 @@ from aiohttp.web_exceptions import HTTPNotFound
 import async_timeout
 
 from homeassistant.components.http import HomeAssistantView
-from homeassistant.core import callback
+from homeassistant.core import HomeAssistant, callback
 from homeassistant.exceptions import HomeAssistantError
 from homeassistant.helpers import config_per_platform, discovery
 from homeassistant.helpers.entity import Entity
 from homeassistant.helpers.entity_component import EntityComponent
+from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 from homeassistant.setup import async_prepare_setup_platform
 
 # mypy: allow-untyped-defs, no-check-untyped-defs
@@ -30,9 +33,9 @@ CONTENT_TYPE_NONE = "none"
 SCAN_INTERVAL = timedelta(seconds=30)
 
 
-async def async_setup(hass, config):
+async def async_setup(hass: HomeAssistant, config: ConfigType) -> bool:
     """Track states and offer events for mailboxes."""
-    mailboxes = []
+    mailboxes: list[Mailbox] = []
     hass.components.frontend.async_register_built_in_panel(
         "mailbox", "mailbox", "mdi:mailbox"
     )
@@ -41,7 +44,11 @@ async def async_setup(hass, config):
     hass.http.register_view(MailboxMediaView(mailboxes))
     hass.http.register_view(MailboxDeleteView(mailboxes))
 
-    async def async_setup_platform(p_type, p_config=None, discovery_info=None):
+    async def async_setup_platform(
+        p_type: str,
+        p_config: ConfigType | None = None,
+        discovery_info: DiscoveryInfoType | None = None,
+    ) -> None:
         """Set up a mailbox platform."""
         if p_config is None:
             p_config = {}
@@ -104,7 +111,7 @@ async def async_setup(hass, config):
 class MailboxEntity(Entity):
     """Entity for each mailbox platform to provide a badge display."""
 
-    def __init__(self, mailbox):
+    def __init__(self, mailbox: Mailbox) -> None:
         """Initialize mailbox entity."""
         self.mailbox = mailbox
         self.message_count = 0
@@ -183,7 +190,7 @@ class StreamError(Exception):
 class MailboxView(HomeAssistantView):
     """Base mailbox view."""
 
-    def __init__(self, mailboxes):
+    def __init__(self, mailboxes: list[Mailbox]) -> None:
         """Initialize a basic mailbox view."""
         self.mailboxes = mailboxes