diff --git a/config/aerc.conf b/config/aerc.conf
index f07900d..3b7b5d6 100644
--- a/config/aerc.conf
+++ b/config/aerc.conf
@@ -179,6 +179,11 @@ completion-popovers=true
 # Default: false
 #force-client-threads=false
 
+# Debounce client-side thread building
+#
+# Default: 50ms
+#client-threads-delay=50ms
+
 [statusline]
 # Describes the format string for the statusline.
 #
diff --git a/config/config.go b/config/config.go
index 6a8be10..233f2e0 100644
--- a/config/config.go
+++ b/config/config.go
@@ -48,6 +48,7 @@ type UIConfig struct {
 	MouseEnabled        bool          `ini:"mouse-enabled"`
 	ThreadingEnabled    bool          `ini:"threading-enabled"`
 	ForceClientThreads  bool          `ini:"force-client-threads"`
+	ClientThreadsDelay  time.Duration `ini:"client-threads-delay"`
 	FuzzyComplete       bool          `ini:"fuzzy-complete"`
 	NewMessageBell      bool          `ini:"new-message-bell"`
 	Spinner             string        `ini:"spinner"`
@@ -712,6 +713,7 @@ func LoadConfigFromFile(root *string) (*AercConfig, error) {
 			EmptyMessage:        "(no messages)",
 			EmptyDirlist:        "(no folders)",
 			MouseEnabled:        false,
+			ClientThreadsDelay:  50 * time.Millisecond,
 			NewMessageBell:      true,
 			FuzzyComplete:       false,
 			Spinner:             "[..]    , [..]   ,  [..]  ,   [..] ,    [..],   [..] ,  [..]  , [..]   ",
diff --git a/lib/msgstore.go b/lib/msgstore.go
index 61a6dd4..9d7f3af 100644
--- a/lib/msgstore.go
+++ b/lib/msgstore.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"git.sr.ht/~rjarry/aerc/lib/sort"
+	"git.sr.ht/~rjarry/aerc/logging"
 	"git.sr.ht/~rjarry/aerc/models"
 	"git.sr.ht/~rjarry/aerc/worker/types"
 )
@@ -53,8 +54,8 @@ type MessageStore struct {
 	triggerNewEmail        func(*models.MessageInfo)
 	triggerDirectoryChange func()
 
-	dirInfoUpdateDebounce *time.Timer
-	dirInfoUpdateDelay    time.Duration
+	threadBuilderDebounce *time.Timer
+	threadBuilderDelay    time.Duration
 }
 
 const MagicUid = 0xFFFFFFFF
@@ -62,12 +63,10 @@ const MagicUid = 0xFFFFFFFF
 func NewMessageStore(worker *types.Worker,
 	dirInfo *models.DirectoryInfo,
 	defaultSortCriteria []*types.SortCriterion,
-	thread bool, clientThreads bool,
+	thread bool, clientThreads bool, clientThreadsDelay time.Duration,
 	triggerNewEmail func(*models.MessageInfo),
 	triggerDirectoryChange func()) *MessageStore {
 
-	dirInfoUpdateDelay := 5 * time.Second
-
 	if !dirInfo.Caps.Thread {
 		clientThreads = true
 	}
@@ -95,8 +94,7 @@ func NewMessageStore(worker *types.Worker,
 		triggerNewEmail:        triggerNewEmail,
 		triggerDirectoryChange: triggerDirectoryChange,
 
-		dirInfoUpdateDelay:    dirInfoUpdateDelay,
-		dirInfoUpdateDebounce: time.NewTimer(dirInfoUpdateDelay),
+		threadBuilderDelay: clientThreadsDelay,
 	}
 }
 
@@ -386,7 +384,17 @@ func (store *MessageStore) runThreadBuilder() {
 			store.builder.Update(msg)
 		}
 	}
-	store.Threads = store.builder.Threads(store.uids)
+	if store.threadBuilderDebounce != nil {
+		if store.threadBuilderDebounce.Stop() {
+			logging.Infof("thread builder debounced")
+		}
+	}
+	store.threadBuilderDebounce = time.AfterFunc(store.threadBuilderDelay, func() {
+		store.Threads = store.builder.Threads(store.uids)
+		if store.onUpdate != nil {
+			store.onUpdate(store)
+		}
+	})
 }
 
 func (store *MessageStore) Delete(uids []uint32,
diff --git a/lib/threadbuilder.go b/lib/threadbuilder.go
index 59abd2f..ce56afe 100644
--- a/lib/threadbuilder.go
+++ b/lib/threadbuilder.go
@@ -1,6 +1,7 @@
 package lib
 
 import (
+	"sync"
 	"time"
 
 	"git.sr.ht/~rjarry/aerc/logging"
@@ -10,6 +11,7 @@ import (
 )
 
 type ThreadBuilder struct {
+	sync.Mutex
 	threadBlocks   map[uint32]jwz.Threadable
 	messageidToUid map[string]uint32
 	seen           map[uint32]bool
@@ -27,6 +29,9 @@ func NewThreadBuilder() *ThreadBuilder {
 
 // Uids returns the uids in threading order
 func (builder *ThreadBuilder) Uids() []uint32 {
+	builder.Lock()
+	defer builder.Unlock()
+
 	if builder.threadedUids == nil {
 		return []uint32{}
 	}
@@ -35,6 +40,9 @@ func (builder *ThreadBuilder) Uids() []uint32 {
 
 // Update updates the thread builder with a new message header
 func (builder *ThreadBuilder) Update(msg *models.MessageInfo) {
+	builder.Lock()
+	defer builder.Unlock()
+
 	if msg != nil {
 		if threadable := newThreadable(msg); threadable != nil {
 			builder.messageidToUid[threadable.MessageThreadID()] = msg.Uid
@@ -45,6 +53,9 @@ func (builder *ThreadBuilder) Update(msg *models.MessageInfo) {
 
 // Threads returns a slice of threads for the given list of uids
 func (builder *ThreadBuilder) Threads(uids []uint32) []*types.Thread {
+	builder.Lock()
+	defer builder.Unlock()
+
 	start := time.Now()
 
 	threads := builder.buildAercThreads(builder.generateStructure(uids), uids)
diff --git a/widgets/account.go b/widgets/account.go
index ff51636..50b0fab 100644
--- a/widgets/account.go
+++ b/widgets/account.go
@@ -288,6 +288,7 @@ func (acct *AccountView) onMessage(msg types.WorkerMessage) {
 				acct.GetSortCriteria(),
 				acct.UiConfig().ThreadingEnabled,
 				acct.UiConfig().ForceClientThreads,
+				acct.UiConfig().ClientThreadsDelay,
 				func(msg *models.MessageInfo) {
 					acct.conf.Triggers.ExecNewEmail(acct.acct,
 						acct.conf, msg)
diff --git a/widgets/msglist.go b/widgets/msglist.go
index 4c7c1c2..95dfa1f 100644
--- a/widgets/msglist.go
+++ b/widgets/msglist.go
@@ -344,6 +344,7 @@ func (ml *MessageList) storeUpdate(store *lib.MessageStore) {
 	if ml.Store() != store {
 		return
 	}
+	ml.Invalidate()
 }
 
 func (ml *MessageList) SetStore(store *lib.MessageStore) {