diff --git a/app/src/androidTest/kotlin/org/libremail/data/local/LibreMailDatabaseTest.kt b/app/src/androidTest/kotlin/org/libremail/data/local/LibreMailDatabaseTest.kt
index 16cbccf..b4ed6cb 100644
--- a/app/src/androidTest/kotlin/org/libremail/data/local/LibreMailDatabaseTest.kt
+++ b/app/src/androidTest/kotlin/org/libremail/data/local/LibreMailDatabaseTest.kt
@@ -53,6 +53,34 @@ class LibreMailDatabaseTest {
         isStarred = false,
     )
 
+    @Test
+    fun observeUnreadCountsAggregatesUnreadSyncedRowsPerAccountAndFolder() = runBlocking {
+        val messageDao = db.messageDao()
+        messageDao.insertNew(
+            listOf(
+                // acct / INBOX: two unread + one read -> counts 2.
+                message("acct:INBOX:1").copy(folder = "INBOX", isRead = false),
+                message("acct:INBOX:2").copy(folder = "INBOX", isRead = false),
+                message("acct:INBOX:3").copy(folder = "INBOX", isRead = true),
+                // acct / Archive: one unread -> counts 1.
+                message("acct:Archive:1").copy(folder = "Archive", isRead = false),
+                // An unread server-search hit (inInbox = false) must never inflate a badge.
+                message("acct:INBOX:search").copy(folder = "INBOX", isRead = false, inInbox = false),
+                // A second account's unread inbox row is counted under its own accountId.
+                message("acct2:INBOX:1").copy(accountId = "acct2", folder = "INBOX", isRead = false),
+            ),
+        )
+
+        val counts = messageDao.observeUnreadCounts().first()
+            .associate { (it.accountId to it.folder) to it.unreadCount }
+
+        assertEquals(2, counts[("acct" to "INBOX")])
+        assertEquals(1, counts[("acct" to "Archive")])
+        assertEquals(1, counts[("acct2" to "INBOX")])
+        // Fully-read folders and search-only rows produce no group at all.
+        assertEquals(3, counts.size)
+    }
+
     @Test
     fun deletingMessageCascadesToItsAttachments() = runBlocking {
         val messageDao = db.messageDao()
diff --git a/app/src/androidTest/kotlin/org/libremail/ui/Fakes.kt b/app/src/androidTest/kotlin/org/libremail/ui/Fakes.kt
index c4dade3..b3adafa 100644
--- a/app/src/androidTest/kotlin/org/libremail/ui/Fakes.kt
+++ b/app/src/androidTest/kotlin/org/libremail/ui/Fakes.kt
@@ -14,6 +14,7 @@ import org.libremail.domain.model.Message
 import org.libremail.domain.model.OutboxMessage
 import org.libremail.domain.model.OutgoingMessage
 import org.libremail.domain.model.ReplyMode
+import org.libremail.domain.model.UnreadCount
 import org.libremail.domain.repository.AccountRepository
 import org.libremail.domain.repository.MailRepository
 import java.io.File
@@ -72,6 +73,7 @@ class FakeMailRepository(
     private val folders: List<Folder> = emptyList(),
     private val attachments: List<Attachment> = emptyList(),
     private val downloadedParts: Set<Int> = emptySet(),
+    private val unreadCounts: List<UnreadCount> = emptyList(),
 ) : MailRepository {
 
     val sentMessages = mutableListOf<OutgoingMessage>()
@@ -93,6 +95,8 @@ class FakeMailRepository(
         },
     )
 
+    override fun observeUnreadCounts(): Flow<List<UnreadCount>> = flowOf(unreadCounts)
+
     override suspend fun refreshFolders(accountId: String): Result<Unit> = Result.success(Unit)
 
     override suspend fun getMessage(id: String): Message? = messages.firstOrNull { it.id == id }
diff --git a/app/src/androidTest/kotlin/org/libremail/ui/mailbox/FolderDrawerTest.kt b/app/src/androidTest/kotlin/org/libremail/ui/mailbox/FolderDrawerTest.kt
index 711d87c..2abb830 100644
--- a/app/src/androidTest/kotlin/org/libremail/ui/mailbox/FolderDrawerTest.kt
+++ b/app/src/androidTest/kotlin/org/libremail/ui/mailbox/FolderDrawerTest.kt
@@ -5,6 +5,7 @@ import androidx.activity.ComponentActivity
 import androidx.compose.material3.ModalDrawerSheet
 import androidx.compose.ui.test.assertIsDisplayed
 import androidx.compose.ui.test.junit4.createAndroidComposeRule
+import androidx.compose.ui.test.onNodeWithContentDescription
 import androidx.compose.ui.test.onNodeWithText
 import androidx.compose.ui.test.performClick
 import androidx.test.ext.junit.runners.AndroidJUnit4
@@ -145,10 +146,34 @@ class FolderDrawerTest {
         assertTrue(unifiedTapped)
     }
 
+    @Test
+    fun folderWithUnreadMail_showsCountBadge_andReadFolderShowsNone() {
+        setContent(
+            accounts = listOf(alice),
+            drawerAccount = alice,
+            folders = listOf(
+                folder("imap:a", "INBOX", "INBOX", FolderRole.INBOX),
+                folder("imap:a", "Archive", "Archive", FolderRole.ARCHIVE),
+            ),
+            folderUnreadCounts = mapOf("INBOX" to 3),
+        )
+
+        // The inbox badge announces its exact count for screen readers.
+        val threeUnread = composeTestRule.activity.resources
+            .getQuantityString(R.plurals.folder_unread_count_description, 3, 3)
+        composeTestRule.onNodeWithContentDescription(threeUnread).assertIsDisplayed()
+        // Archive has no unread mail, so no badge is rendered for it.
+        val oneUnread = composeTestRule.activity.resources
+            .getQuantityString(R.plurals.folder_unread_count_description, 1, 1)
+        composeTestRule.onNodeWithContentDescription(oneUnread).assertDoesNotExist()
+    }
+
     private fun setContent(
         accounts: List<Account>,
         drawerAccount: Account?,
         folders: List<Folder>,
+        folderUnreadCounts: Map<String, Int> = emptyMap(),
+        accountsWithUnread: Set<String> = emptySet(),
         selectedAccountId: String? = null,
         selectedFolder: String = "INBOX",
         onSelectUnifiedInbox: () -> Unit = {},
@@ -162,6 +187,8 @@ class FolderDrawerTest {
                         accounts = accounts,
                         drawerAccount = drawerAccount,
                         folders = folders,
+                        folderUnreadCounts = folderUnreadCounts,
+                        accountsWithUnread = accountsWithUnread,
                         selectedAccountId = selectedAccountId,
                         selectedFolder = selectedFolder,
                         onSelectUnifiedInbox = onSelectUnifiedInbox,
diff --git a/app/src/main/kotlin/org/libremail/data/local/Mappers.kt b/app/src/main/kotlin/org/libremail/data/local/Mappers.kt
index 3247fbe..c05bbb9 100644
--- a/app/src/main/kotlin/org/libremail/data/local/Mappers.kt
+++ b/app/src/main/kotlin/org/libremail/data/local/Mappers.kt
@@ -8,6 +8,7 @@ import org.libremail.data.local.entity.AccountSettingsEntity
 import org.libremail.data.local.entity.AttachmentEntity
 import org.libremail.data.local.entity.DraftEntity
 import org.libremail.data.local.entity.FolderEntity
+import org.libremail.data.local.entity.FolderUnreadCount
 import org.libremail.data.local.entity.MessageEntity
 import org.libremail.data.local.entity.MessageSummary
 import org.libremail.data.local.entity.OutboxEntity
@@ -26,6 +27,7 @@ import org.libremail.domain.model.OutboxMessage
 import org.libremail.domain.model.OutgoingAttachment
 import org.libremail.domain.model.ServerConfig
 import org.libremail.domain.model.SmtpParams
+import org.libremail.domain.model.UnreadCount
 import org.libremail.mail.AttachmentPart
 import org.libremail.mail.FetchedFolder
 import org.libremail.mail.FetchedMessage
@@ -168,6 +170,12 @@ internal fun FetchedFolder.toEntity(accountId: String, sortOrder: Int): FolderEn
     specialUse = FolderRole.isServerSpecial(attributes),
 )
 
+internal fun FolderUnreadCount.toDomain(): UnreadCount = UnreadCount(
+    accountId = accountId,
+    folder = folder,
+    count = unreadCount,
+)
+
 internal fun AttachmentEntity.toDomain(): Attachment = Attachment(
     messageId = messageId,
     partIndex = partIndex,
diff --git a/app/src/main/kotlin/org/libremail/data/local/dao/MessageDao.kt b/app/src/main/kotlin/org/libremail/data/local/dao/MessageDao.kt
index dfc556c..b0399cc 100644
--- a/app/src/main/kotlin/org/libremail/data/local/dao/MessageDao.kt
+++ b/app/src/main/kotlin/org/libremail/data/local/dao/MessageDao.kt
@@ -6,6 +6,7 @@ import androidx.room.Insert
 import androidx.room.OnConflictStrategy
 import androidx.room.Query
 import kotlinx.coroutines.flow.Flow
+import org.libremail.data.local.entity.FolderUnreadCount
 import org.libremail.data.local.entity.MessageEntity
 import org.libremail.data.local.entity.MessageSummary
 
@@ -23,6 +24,19 @@ interface MessageDao {
     )
     fun observeSummaries(): Flow<List<MessageSummary>>
 
+    /**
+     * Live per-(account, folder) unread counts for the drawer's folder badges and the bold styling of
+     * accounts with unread mail. Counts only folder-synced rows (`inInbox = 1`), so transient
+     * server-search hits never inflate a badge; read rows and folders with no unread mail are simply
+     * absent from the result. A pure `COUNT(*)` aggregate — no message rows are pulled into memory —
+     * whose `GROUP BY accountId, folder` is served by the existing `(accountId, folder, uid)` index.
+     */
+    @Query(
+        "SELECT accountId, folder, COUNT(*) AS unreadCount FROM messages " +
+            "WHERE inInbox = 1 AND isRead = 0 GROUP BY accountId, folder",
+    )
+    fun observeUnreadCounts(): Flow<List<FolderUnreadCount>>
+
     @Query("SELECT * FROM messages WHERE id = :id LIMIT 1")
     suspend fun getById(id: String): MessageEntity?
 
diff --git a/app/src/main/kotlin/org/libremail/data/local/entity/FolderUnreadCount.kt b/app/src/main/kotlin/org/libremail/data/local/entity/FolderUnreadCount.kt
new file mode 100644
index 0000000..9f53a00
--- /dev/null
+++ b/app/src/main/kotlin/org/libremail/data/local/entity/FolderUnreadCount.kt
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.data.local.entity
+
+/**
+ * Aggregate projection of [MessageEntity] counting unread, folder-synced rows per (account, folder).
+ * Produced by `MessageDao.observeUnreadCounts`' `GROUP BY` query — never a stored table — so the
+ * counts come straight from SQLite without pulling any message rows into memory.
+ */
+data class FolderUnreadCount(val accountId: String, val folder: String, val unreadCount: Int)
diff --git a/app/src/main/kotlin/org/libremail/data/repository/MailRepositoryImpl.kt b/app/src/main/kotlin/org/libremail/data/repository/MailRepositoryImpl.kt
index ba3f629..61ff531 100644
--- a/app/src/main/kotlin/org/libremail/data/repository/MailRepositoryImpl.kt
+++ b/app/src/main/kotlin/org/libremail/data/repository/MailRepositoryImpl.kt
@@ -36,6 +36,7 @@ import org.libremail.domain.model.OutboxMessage
 import org.libremail.domain.model.OutgoingAttachment
 import org.libremail.domain.model.OutgoingMessage
 import org.libremail.domain.model.ReplyMode
+import org.libremail.domain.model.UnreadCount
 import org.libremail.domain.repository.MailRepository
 import org.libremail.mail.ImapClient
 import java.io.File
@@ -68,6 +69,10 @@ class MailRepositoryImpl @Inject constructor(
             rows.map { it.toDomain() }
         }
 
+    override fun observeUnreadCounts(): Flow<List<UnreadCount>> = messageDao.observeUnreadCounts().map { rows ->
+        rows.map { it.toDomain() }
+    }
+
     override suspend fun refreshFolders(accountId: String): Result<Unit> = runCatching {
         val account = accountDao.getById(accountId)?.toDomain() ?: error("Account not found")
         val params = connectionFactory.imapParamsFor(account)
diff --git a/app/src/main/kotlin/org/libremail/domain/model/UnreadCount.kt b/app/src/main/kotlin/org/libremail/domain/model/UnreadCount.kt
new file mode 100644
index 0000000..3e0db33
--- /dev/null
+++ b/app/src/main/kotlin/org/libremail/domain/model/UnreadCount.kt
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.domain.model
+
+/**
+ * The number of unread, folder-synced messages in one account's folder. Emitted per (account, folder)
+ * pair that currently holds unread mail; pairs with no unread mail are simply absent. Feeds the
+ * drawer's per-folder unread badges (#83) and the bold styling of accounts that have unread mail (#84).
+ */
+data class UnreadCount(val accountId: String, val folder: String, val count: Int)
diff --git a/app/src/main/kotlin/org/libremail/domain/repository/MailRepository.kt b/app/src/main/kotlin/org/libremail/domain/repository/MailRepository.kt
index 1a761b5..4126fc6 100644
--- a/app/src/main/kotlin/org/libremail/domain/repository/MailRepository.kt
+++ b/app/src/main/kotlin/org/libremail/domain/repository/MailRepository.kt
@@ -9,6 +9,7 @@ import org.libremail.domain.model.Message
 import org.libremail.domain.model.OutboxMessage
 import org.libremail.domain.model.OutgoingMessage
 import org.libremail.domain.model.ReplyMode
+import org.libremail.domain.model.UnreadCount
 import java.io.File
 
 /**
@@ -21,6 +22,13 @@ interface MailRepository {
     /** The account's cached IMAP folders for the navigation drawer. */
     fun observeFolders(accountId: String): Flow<List<Folder>>
 
+    /**
+     * Live per-(account, folder) unread counts across every account, for the drawer's folder badges
+     * and the bold styling of accounts with unread mail. Only (account, folder) pairs that currently
+     * hold unread, folder-synced mail are emitted.
+     */
+    fun observeUnreadCounts(): Flow<List<UnreadCount>>
+
     /** Refreshes the account's folder list from the server into the cache. */
     suspend fun refreshFolders(accountId: String): Result<Unit>
 
diff --git a/app/src/main/kotlin/org/libremail/ui/mailbox/FolderDrawer.kt b/app/src/main/kotlin/org/libremail/ui/mailbox/FolderDrawer.kt
index de9a918..8695334 100644
--- a/app/src/main/kotlin/org/libremail/ui/mailbox/FolderDrawer.kt
+++ b/app/src/main/kotlin/org/libremail/ui/mailbox/FolderDrawer.kt
@@ -27,7 +27,11 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.vector.ImageVector
+import androidx.compose.ui.res.pluralStringResource
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.clearAndSetSemantics
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import org.libremail.R
@@ -37,13 +41,17 @@ import org.libremail.domain.model.FolderRole
 
 /**
  * The navigation drawer's contents: an optional account switcher and "All Inboxes" entry (only with
- * 2+ accounts), then the drawer account's folders — standard folders (Inbox, Sent, …) first.
+ * 2+ accounts), then the drawer account's folders — standard folders (Inbox, Sent, …) first. Each
+ * folder shows its unread count as a trailing badge ([folderUnreadCounts]), and accounts with unread
+ * mail ([accountsWithUnread]) render their email in bold.
  */
 @Composable
 fun FolderDrawer(
     accounts: List<Account>,
     drawerAccount: Account?,
     folders: List<Folder>,
+    folderUnreadCounts: Map<String, Int>,
+    accountsWithUnread: Set<String>,
     selectedAccountId: String?,
     selectedFolder: String,
     onSelectUnifiedInbox: () -> Unit,
@@ -63,7 +71,7 @@ fun FolderDrawer(
         )
 
         if (accounts.size >= 2 && drawerAccount != null) {
-            AccountSwitcher(accounts, drawerAccount, onSelectDrawerAccount)
+            AccountSwitcher(accounts, drawerAccount, accountsWithUnread, onSelectDrawerAccount)
             NavigationDrawerItem(
                 label = { Text(stringResource(R.string.folder_all_inboxes)) },
                 icon = { Icon(Icons.Filled.Email, contentDescription = null) },
@@ -87,9 +95,15 @@ fun FolderDrawer(
             val iconContent: (@Composable () -> Unit)? = folderIcon(folder.role)?.let { vector ->
                 { Icon(vector, contentDescription = null) }
             }
+            val unread = folderUnreadCounts[folder.fullName] ?: 0
             NavigationDrawerItem(
                 label = { Text(resolvedLabels[folder.fullName] ?: folderDisplayLabel(folder)) },
                 icon = iconContent,
+                badge = if (unread > 0) {
+                    { UnreadBadgeLabel(unread) }
+                } else {
+                    null
+                },
                 selected = isSelected,
                 onClick = {
                     if (folder.selectable && drawerAccount != null) {
@@ -103,19 +117,34 @@ fun FolderDrawer(
 }
 
 @Composable
-private fun AccountSwitcher(accounts: List<Account>, current: Account, onSelect: (String) -> Unit) {
+private fun AccountSwitcher(
+    accounts: List<Account>,
+    current: Account,
+    accountsWithUnread: Set<String>,
+    onSelect: (String) -> Unit,
+) {
     var expanded by remember { mutableStateOf(false) }
     TextButton(
         onClick = { expanded = true },
         modifier = Modifier.padding(horizontal = 16.dp),
     ) {
-        Text(current.email, maxLines = 1, overflow = TextOverflow.Ellipsis)
+        Text(
+            current.email,
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+            fontWeight = if (current.id in accountsWithUnread) FontWeight.Bold else FontWeight.Normal,
+        )
         Icon(Icons.Filled.ArrowDropDown, contentDescription = stringResource(R.string.drawer_switch_account))
     }
     DropdownMenu(expanded = expanded, onDismissRequest = { expanded = false }) {
         accounts.forEach { account ->
             DropdownMenuItem(
-                text = { Text(account.email) },
+                text = {
+                    Text(
+                        account.email,
+                        fontWeight = if (account.id in accountsWithUnread) FontWeight.Bold else FontWeight.Normal,
+                    )
+                },
                 onClick = {
                     onSelect(account.id)
                     expanded = false
@@ -125,6 +154,29 @@ private fun AccountSwitcher(accounts: List<Account>, current: Account, onSelect:
     }
 }
 
+/** Cap for a folder's visible unread badge; higher counts render as "99+" to keep the row compact. */
+private const val UNREAD_BADGE_CAP = 99
+
+/**
+ * A folder row's trailing unread-count badge. The visible label is capped at [UNREAD_BADGE_CAP] as
+ * "99+" so a large count can't blow out the row, while the semantics announce the exact count as
+ * "N unread messages" (overriding the terse glyph) for screen readers.
+ */
+@Composable
+private fun UnreadBadgeLabel(count: Int) {
+    val display = if (count > UNREAD_BADGE_CAP) {
+        stringResource(R.string.folder_unread_overflow)
+    } else {
+        count.toString()
+    }
+    val description = pluralStringResource(R.plurals.folder_unread_count_description, count, count)
+    Text(
+        text = display,
+        style = MaterialTheme.typography.labelMedium,
+        modifier = Modifier.clearAndSetSemantics { contentDescription = description },
+    )
+}
+
 /**
  * De-duplicated display labels for [folders], keyed by [Folder.fullName] — the one resolution used
  * by the drawer, the move-to picker, and the app-bar title, so a folder reads the same everywhere.
diff --git a/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxScreen.kt b/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxScreen.kt
index fc4f1aa..663aeaa 100644
--- a/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxScreen.kt
+++ b/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxScreen.kt
@@ -106,6 +106,8 @@ fun MailboxScreen(
     val selectedAccountId by viewModel.selectedAccountId.collectAsStateWithLifecycle()
     val selectedFolder by viewModel.selectedFolder.collectAsStateWithLifecycle()
     val folders by viewModel.folders.collectAsStateWithLifecycle()
+    val folderUnreadCounts by viewModel.folderUnreadCounts.collectAsStateWithLifecycle()
+    val accountsWithUnread by viewModel.accountsWithUnread.collectAsStateWithLifecycle()
     val drawerAccount by viewModel.drawerAccount.collectAsStateWithLifecycle()
     val hasAccounts by viewModel.hasAccounts.collectAsStateWithLifecycle()
     val draftCount by viewModel.draftCount.collectAsStateWithLifecycle()
@@ -156,6 +158,8 @@ fun MailboxScreen(
                     accounts = accounts,
                     drawerAccount = drawerAccount,
                     folders = folders,
+                    folderUnreadCounts = folderUnreadCounts,
+                    accountsWithUnread = accountsWithUnread,
                     selectedAccountId = selectedAccountId,
                     selectedFolder = selectedFolder,
                     onSelectUnifiedInbox = {
@@ -256,6 +260,7 @@ fun MailboxScreen(
                             AccountFilterRow(
                                 accounts = accounts,
                                 selectedId = selectedAccountId,
+                                accountsWithUnread = accountsWithUnread,
                                 onSelect = viewModel::selectAccount,
                             )
                         }
@@ -411,7 +416,12 @@ private fun OutboxEntry(count: Int, onClick: () -> Unit) {
 }
 
 @Composable
-private fun AccountFilterRow(accounts: List<Account>, selectedId: String?, onSelect: (String?) -> Unit) {
+private fun AccountFilterRow(
+    accounts: List<Account>,
+    selectedId: String?,
+    accountsWithUnread: Set<String>,
+    onSelect: (String?) -> Unit,
+) {
     Row(
         modifier = Modifier
             .fillMaxWidth()
@@ -428,7 +438,13 @@ private fun AccountFilterRow(accounts: List<Account>, selectedId: String?, onSel
             FilterChip(
                 selected = selectedId == account.id,
                 onClick = { onSelect(account.id) },
-                label = { Text(account.email, maxLines = 1) },
+                label = {
+                    Text(
+                        account.email,
+                        maxLines = 1,
+                        fontWeight = if (account.id in accountsWithUnread) FontWeight.Bold else FontWeight.Normal,
+                    )
+                },
             )
         }
     }
diff --git a/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxViewModel.kt b/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxViewModel.kt
index 180b9a4..d2d60fd 100644
--- a/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxViewModel.kt
+++ b/app/src/main/kotlin/org/libremail/ui/mailbox/MailboxViewModel.kt
@@ -28,6 +28,7 @@ import org.libremail.domain.model.Folder
 import org.libremail.domain.model.FolderRole
 import org.libremail.domain.model.Message
 import org.libremail.domain.model.ReplyMode
+import org.libremail.domain.model.UnreadCount
 import org.libremail.domain.repository.AccountRepository
 import org.libremail.domain.repository.MailRepository
 import org.libremail.ui.navigation.Routes
@@ -87,6 +88,28 @@ class MailboxViewModel @Inject constructor(
         }
         .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyList())
 
+    /**
+     * Live unread counts across every account, shared by the two drawer indicators below so the
+     * underlying `COUNT` query is collected once no matter how many observers derive from it.
+     */
+    private val unreadCounts: StateFlow<List<UnreadCount>> = mailRepository.observeUnreadCounts()
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyList())
+
+    /** #83: unread-message count keyed by folder full name for the drawer account (absent = none). */
+    val folderUnreadCounts: StateFlow<Map<String, Int>> =
+        combine(drawerAccount, unreadCounts) { account, counts ->
+            if (account == null) {
+                emptyMap()
+            } else {
+                counts.filter { it.accountId == account.id }.associate { it.folder to it.count }
+            }
+        }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptyMap())
+
+    /** #84: ids of accounts that currently have unread mail in any folder. */
+    val accountsWithUnread: StateFlow<Set<String>> = unreadCounts
+        .map { counts -> counts.filter { it.count > 0 }.map { it.accountId }.toSet() }
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), emptySet())
+
     private val _searchActive = MutableStateFlow(false)
     val searchActive: StateFlow<Boolean> = _searchActive.asStateFlow()
 
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 9b713a0..75f6c41 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -68,6 +68,13 @@
     <string name="folder_archive">Archive</string>
     <string name="folder_spam">Spam</string>
     <string name="folder_trash">Trash</string>
+    <!-- Unread badge shown after a folder name; caps very large counts. -->
+    <string name="folder_unread_overflow">99+</string>
+    <!-- Screen-reader description for a folder's unread badge, e.g. "12 unread messages". -->
+    <plurals name="folder_unread_count_description">
+        <item quantity="one">%1$d unread message</item>
+        <item quantity="other">%1$d unread messages</item>
+    </plurals>
 
     <!-- Compose -->
     <string name="compose_from">From</string>
diff --git a/app/src/test/kotlin/org/libremail/ui/mailbox/MailboxViewModelTest.kt b/app/src/test/kotlin/org/libremail/ui/mailbox/MailboxViewModelTest.kt
index b73e4dd..02d2699 100644
--- a/app/src/test/kotlin/org/libremail/ui/mailbox/MailboxViewModelTest.kt
+++ b/app/src/test/kotlin/org/libremail/ui/mailbox/MailboxViewModelTest.kt
@@ -30,6 +30,7 @@ import org.libremail.domain.model.MailSecurity
 import org.libremail.domain.model.Message
 import org.libremail.domain.model.ReplyMode
 import org.libremail.domain.model.ServerConfig
+import org.libremail.domain.model.UnreadCount
 import org.libremail.domain.repository.AccountRepository
 import org.libremail.domain.repository.MailRepository
 import org.libremail.ui.navigation.Routes
@@ -429,10 +430,55 @@ class MailboxViewModelTest {
         assertEquals(listOf("imap:a:INBOX:1"), vm.messages.value.map { it.id })
     }
 
+    @Test
+    fun `folderUnreadCounts maps the drawer account's folders to their unread counts`() = runTest(testDispatcher) {
+        val vm = createViewModel(
+            accounts = listOf(alice, bob),
+            messages = emptyList(),
+            unreadCounts = listOf(
+                UnreadCount("imap:a", "INBOX", 3),
+                UnreadCount("imap:a", "[Gmail]/Spam", 1),
+                UnreadCount("imap:b", "INBOX", 9),
+            ),
+        )
+        backgroundScope.launch { vm.folderUnreadCounts.collect {} }
+
+        // The drawer defaults to the first account (alice); bob's counts are excluded.
+        assertEquals(mapOf("INBOX" to 3, "[Gmail]/Spam" to 1), vm.folderUnreadCounts.value)
+    }
+
+    @Test
+    fun `folderUnreadCounts follows the drawer-account switch`() = runTest(testDispatcher) {
+        val vm = createViewModel(
+            accounts = listOf(alice, bob),
+            messages = emptyList(),
+            unreadCounts = listOf(UnreadCount("imap:a", "INBOX", 3), UnreadCount("imap:b", "INBOX", 9)),
+        )
+        backgroundScope.launch { vm.folderUnreadCounts.collect {} }
+
+        vm.setDrawerAccount("imap:b")
+
+        assertEquals(mapOf("INBOX" to 9), vm.folderUnreadCounts.value)
+    }
+
+    @Test
+    fun `accountsWithUnread lists every account that has unread mail in any folder`() = runTest(testDispatcher) {
+        val vm = createViewModel(
+            accounts = listOf(alice, bob),
+            messages = emptyList(),
+            // alice has unread mail (in a non-inbox folder too); bob has none.
+            unreadCounts = listOf(UnreadCount("imap:a", "INBOX", 3), UnreadCount("imap:a", "Archive", 2)),
+        )
+        backgroundScope.launch { vm.accountsWithUnread.collect {} }
+
+        assertEquals(setOf("imap:a"), vm.accountsWithUnread.value)
+    }
+
     private fun createViewModel(
         accounts: List<Account>,
         messages: List<Message>,
         folders: Map<String, List<Folder>> = emptyMap(),
+        unreadCounts: List<UnreadCount> = emptyList(),
         syncer: MailSyncer = mockk(relaxed = true),
         repo: MailRepository = mockk(relaxed = true),
         initialAccountId: String? = null,
@@ -440,6 +486,7 @@ class MailboxViewModelTest {
         every { repo.observeMessages() } returns MutableStateFlow(messages)
         every { repo.observeDrafts() } returns flowOf(emptyList())
         every { repo.observeOutbox() } returns flowOf(emptyList())
+        every { repo.observeUnreadCounts() } returns MutableStateFlow(unreadCounts)
         accounts.forEach { account ->
             every { repo.observeFolders(account.id) } returns MutableStateFlow(folders[account.id] ?: emptyList())
         }