diff --git a/CHANGELOG.md b/CHANGELOG.md
index bffcb1b7..b068e84f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
 
 ## Fixed
 - DAV: `acl-principal-prop-set` REPORT enforced the wrong privilege.
+- JMAP: `Thread/get` did not filter by per-mailbox ACLs on shared accounts.
 
 
 ## [0.16.5] - 2026-05-11
diff --git a/crates/common/src/network/dns/update.rs b/crates/common/src/network/dns/update.rs
index 86173203..74e808cb 100644
--- a/crates/common/src/network/dns/update.rs
+++ b/crates/common/src/network/dns/update.rs
@@ -47,11 +47,11 @@ impl DnsUpdater {
                 core,
                 updater: dns_update::DnsUpdater::new_rfc2136_tsig(
                     match server.protocol {
-                        enums::IpProtocol::Udp => DnsAddress::Tcp(SocketAddr::new(
+                        enums::IpProtocol::Tcp => DnsAddress::Tcp(SocketAddr::new(
                             server.host.into_inner(),
                             server.port as u16,
                         )),
-                        enums::IpProtocol::Tcp => DnsAddress::Udp(SocketAddr::new(
+                        enums::IpProtocol::Udp => DnsAddress::Udp(SocketAddr::new(
                             server.host.into_inner(),
                             server.port as u16,
                         )),
diff --git a/crates/jmap/src/api/request.rs b/crates/jmap/src/api/request.rs
index 5a7cb288..f391b9ef 100644
--- a/crates/jmap/src/api/request.rs
+++ b/crates/jmap/src/api/request.rs
@@ -247,7 +247,7 @@ impl RequestHandler for Server {
                     set_account_id_if_missing(&mut req.account_id, access_token);
                     access_token.assert_has_access(req.account_id, Collection::Email)?;
 
-                    self.thread_get(*req).await?.into()
+                    self.thread_get(*req, access_token).await?.into()
                 }
                 GetRequestMethod::Identity(mut req) => {
                     set_account_id_if_missing(&mut req.account_id, access_token);
diff --git a/crates/jmap/src/thread/get.rs b/crates/jmap/src/thread/get.rs
index 56f673c2..75599c33 100644
--- a/crates/jmap/src/thread/get.rs
+++ b/crates/jmap/src/thread/get.rs
@@ -5,8 +5,8 @@
  */
 
 use crate::changes::state::StateManager;
-use common::Server;
-use email::cache::MessageCacheFetch;
+use common::{Server, auth::AccessToken};
+use email::cache::{MessageCacheFetch, email::MessageCacheAccess};
 use jmap_proto::{
     method::get::{GetRequest, GetResponse},
     object::thread::{Thread, ThreadProperty, ThreadValue},
@@ -21,12 +21,13 @@ use store::{
     write::SearchIndex,
 };
 use trc::AddContext;
-use types::{collection::SyncCollection, id::Id};
+use types::{acl::Acl, collection::SyncCollection, id::Id};
 
 pub trait ThreadGet: Sync + Send {
     fn thread_get(
         &self,
         request: GetRequest<Thread>,
+        access_token: &AccessToken,
     ) -> impl Future<Output = trc::Result<GetResponse<Thread>>> + Send;
 }
 
@@ -34,17 +35,27 @@ impl ThreadGet for Server {
     async fn thread_get(
         &self,
         mut request: GetRequest<Thread>,
+        access_token: &AccessToken,
     ) -> trc::Result<GetResponse<Thread>> {
         let account_id = request.account_id.document_id();
-        let mut thread_map: AHashMap<u32, RoaringBitmap> = AHashMap::with_capacity(32);
-        let mut all_ids = RoaringBitmap::new();
-        for item in &self
+        let cache = self
             .get_cached_messages(account_id)
             .await
-            .caused_by(trc::location!())?
-            .emails
-            .items
-        {
+            .caused_by(trc::location!())?;
+        let shared_ids = if access_token.is_shared(account_id) {
+            Some(cache.shared_messages(access_token, Acl::ReadItems))
+        } else {
+            None
+        };
+        let mut thread_map: AHashMap<u32, RoaringBitmap> = AHashMap::with_capacity(32);
+        let mut all_ids = RoaringBitmap::new();
+        for item in &cache.emails.items {
+            if shared_ids
+                .as_ref()
+                .is_some_and(|ids| !ids.contains(item.document_id))
+            {
+                continue;
+            }
             thread_map
                 .entry(item.thread_id)
                 .or_default()