diff --git a/src/backends/id_mapper.rs b/src/backends/id_mapper.rs
index 7ca77a1..953a729 100644
--- a/src/backends/id_mapper.rs
+++ b/src/backends/id_mapper.rs
@@ -76,42 +76,39 @@ impl IdMapper {
     }
 
     pub fn append(&mut self, lines: Vec<(String, String)>) -> Result<usize> {
-        let mut entries = String::new();
+        self.extend(lines);
 
-        self.extend(lines.clone());
+        let mut entries = String::new();
+        let mut short_hash_len = self.short_hash_len;
 
         for (hash, id) in self.iter() {
-            entries.push_str(&format!("{} {}\n", hash, id));
-        }
-
-        for (hash, id) in lines {
             loop {
                 let short_hash = &hash[0..self.short_hash_len];
                 let conflict_found = self
                     .map
                     .keys()
-                    .find(|cached_hash| {
-                        cached_hash.starts_with(short_hash) && *cached_hash != &hash
-                    })
+                    .find(|cached_hash| cached_hash.starts_with(short_hash) && cached_hash != &hash)
                     .is_some();
                 if self.short_hash_len > 32 || !conflict_found {
                     break;
                 }
-                self.short_hash_len += 1;
+                short_hash_len += 1;
             }
             entries.push_str(&format!("{} {}\n", hash, id));
         }
 
+        self.short_hash_len = short_hash_len;
+
         OpenOptions::new()
             .write(true)
             .create(true)
             .truncate(true)
             .open(&self.path)
             .context("cannot open maildir id hash map cache")?
-            .write(format!("{}\n{}", self.short_hash_len, entries).as_bytes())
+            .write(format!("{}\n{}", short_hash_len, entries).as_bytes())
             .context("cannot write maildir id hash map cache")?;
 
-        Ok(self.short_hash_len)
+        Ok(short_hash_len)
     }
 }
 
diff --git a/src/backends/maildir/maildir_backend.rs b/src/backends/maildir/maildir_backend.rs
index c3e64b4..2bf3a9c 100644
--- a/src/backends/maildir/maildir_backend.rs
+++ b/src/backends/maildir/maildir_backend.rs
@@ -54,6 +54,12 @@ impl<'a> MaildirBackend<'a> {
                     // maildir subdirectory by adding a "." in front
                     // of the name as described in the spec:
                     // https://cr.yp.to/proto/maildir.html
+                    let dir = self
+                        .account_config
+                        .mailboxes
+                        .get(dir)
+                        .map(|s| s.as_str())
+                        .unwrap_or(dir);
                     let path = self.mdir.path().join(format!(".{}", dir));
                     self.validate_mdir_path(path)
                 })
diff --git a/src/backends/notmuch/notmuch_backend.rs b/src/backends/notmuch/notmuch_backend.rs
index 6393d68..416e1c0 100644
--- a/src/backends/notmuch/notmuch_backend.rs
+++ b/src/backends/notmuch/notmuch_backend.rs
@@ -193,24 +193,16 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
         Ok(envelopes)
     }
 
-    fn add_msg(&mut self, dir: &str, msg: &[u8], tags: &str) -> Result<Box<dyn ToString>> {
+    fn add_msg(&mut self, _: &str, msg: &[u8], tags: &str) -> Result<Box<dyn ToString>> {
         info!(">> add notmuch envelopes");
-        debug!("dir: {:?}", dir);
         debug!("tags: {:?}", tags);
 
-        let mdir = self
-            .mdir
-            .get_mdir_from_dir(dir)
-            .with_context(|| format!("cannot get maildir instance from {:?}", dir))?;
-        let mdir_path_str = mdir
-            .path()
-            .to_str()
-            .ok_or_else(|| anyhow!("cannot parse maildir path to string"))?;
+        let dir = &self.notmuch_config.notmuch_database_dir;
 
         // Adds the message to the maildir folder and gets its hash.
         let hash = self
             .mdir
-            .add_msg(mdir_path_str, msg, "seen")
+            .add_msg("inbox", msg, "seen")
             .with_context(|| {
                 format!(
                     "cannot add notmuch message to maildir {:?}",
@@ -222,12 +214,13 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
 
         // Retrieves the file path of the added message by its maildir
         // identifier.
-        let id = IdMapper::new(mdir.path())
-            .with_context(|| format!("cannot create id mapper instance for {:?}", dir))?
+        let mut mapper = IdMapper::new(dir)
+            .with_context(|| format!("cannot create id mapper instance for {:?}", dir))?;
+        let id = mapper
             .find(&hash)
             .with_context(|| format!("cannot find notmuch message from short hash {:?}", hash))?;
         debug!("id: {:?}", id);
-        let file_path = mdir.path().join("cur").join(format!("{}:2,S", id));
+        let file_path = dir.join("cur").join(format!("{}:2,S", id));
         debug!("file path: {:?}", file_path);
 
         // Adds the message to the notmuch database by indexing it.
@@ -240,13 +233,6 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
         let hash = format!("{:x}", md5::compute(&id));
 
         // Appends hash entry to the id mapper cache file.
-        let mut mapper =
-            IdMapper::new(&self.notmuch_config.notmuch_database_dir).with_context(|| {
-                format!(
-                    "cannot create id mapper instance for {:?}",
-                    self.notmuch_config.notmuch_database_dir
-                )
-            })?;
         mapper
             .append(vec![(hash.clone(), id.clone())])
             .with_context(|| {
@@ -264,7 +250,7 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
         Ok(Box::new(hash))
     }
 
-    fn get_msg(&mut self, _virt_mbox: &str, short_hash: &str) -> Result<Msg> {
+    fn get_msg(&mut self, _: &str, short_hash: &str) -> Result<Msg> {
         info!(">> add notmuch envelopes");
         debug!("short hash: {:?}", short_hash);
 
@@ -300,7 +286,7 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
         Ok(msg)
     }
 
-    fn copy_msg(&mut self, _mbox_src: &str, _mbox_dst: &str, _id: &str) -> Result<()> {
+    fn copy_msg(&mut self, _dir_src: &str, _dir_dst: &str, _short_hash: &str) -> Result<()> {
         info!(">> copy notmuch message");
         info!("<< copy notmuch message");
         Err(anyhow!(
@@ -308,7 +294,7 @@ impl<'a> Backend<'a> for NotmuchBackend<'a> {
         ))
     }
 
-    fn move_msg(&mut self, _src: &str, _dst: &str, _id: &str) -> Result<()> {
+    fn move_msg(&mut self, _dir_src: &str, _dir_dst: &str, _short_hash: &str) -> Result<()> {
         info!(">> move notmuch message");
         info!("<< move notmuch message");
         Err(anyhow!(
diff --git a/tests/test_maildir_backend.rs b/tests/test_maildir_backend.rs
index adcc2e2..d998789 100644
--- a/tests/test_maildir_backend.rs
+++ b/tests/test_maildir_backend.rs
@@ -19,7 +19,10 @@ fn test_maildir_backend() {
 
     // configure accounts
     let account_config = AccountConfig {
-        mailboxes: HashMap::from_iter([("inbox".into(), "INBOX".into())]),
+        mailboxes: HashMap::from_iter([
+            ("inbox".into(), "INBOX".into()),
+            ("subdir".into(), "Subdir".into()),
+        ]),
         ..AccountConfig::default()
     };
     let mdir_config = MaildirBackendConfig {
@@ -33,16 +36,16 @@ fn test_maildir_backend() {
 
     // check that a message can be added
     let msg = include_bytes!("./emails/alice-to-patrick.eml");
-    let hash = mdir.add_msg("INBOX", msg, "seen").unwrap().to_string();
+    let hash = mdir.add_msg("inbox", msg, "seen").unwrap().to_string();
 
     // check that the added message exists
-    let msg = mdir.get_msg("INBOX", &hash).unwrap();
+    let msg = mdir.get_msg("inbox", &hash).unwrap();
     assert_eq!("alice@localhost", msg.from.clone().unwrap().to_string());
     assert_eq!("patrick@localhost", msg.to.clone().unwrap().to_string());
     assert_eq!("Ceci est un message.", msg.fold_text_plain_parts());
 
     // check that the envelope of the added message exists
-    let envelopes = mdir.get_envelopes("INBOX", 10, 0).unwrap();
+    let envelopes = mdir.get_envelopes("inbox", 10, 0).unwrap();
     let envelopes: &MaildirEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert_eq!(1, envelopes.len());
@@ -50,9 +53,9 @@ fn test_maildir_backend() {
     assert_eq!("Plain message", envelope.subject);
 
     // check that a flag can be added to the message
-    mdir.add_flags("INBOX", &envelope.hash, "flagged passed")
+    mdir.add_flags("inbox", &envelope.hash, "flagged passed")
         .unwrap();
-    let envelopes = mdir.get_envelopes("INBOX", 1, 0).unwrap();
+    let envelopes = mdir.get_envelopes("inbox", 1, 0).unwrap();
     let envelopes: &MaildirEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(envelope.flags.contains(&MaildirFlag::Seen));
@@ -60,8 +63,8 @@ fn test_maildir_backend() {
     assert!(envelope.flags.contains(&MaildirFlag::Passed));
 
     // check that the message flags can be changed
-    mdir.set_flags("INBOX", &envelope.hash, "passed").unwrap();
-    let envelopes = mdir.get_envelopes("INBOX", 1, 0).unwrap();
+    mdir.set_flags("inbox", &envelope.hash, "passed").unwrap();
+    let envelopes = mdir.get_envelopes("inbox", 1, 0).unwrap();
     let envelopes: &MaildirEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(!envelope.flags.contains(&MaildirFlag::Seen));
@@ -69,8 +72,8 @@ fn test_maildir_backend() {
     assert!(envelope.flags.contains(&MaildirFlag::Passed));
 
     // check that a flag can be removed from the message
-    mdir.del_flags("INBOX", &envelope.hash, "passed").unwrap();
-    let envelopes = mdir.get_envelopes("INBOX", 1, 0).unwrap();
+    mdir.del_flags("inbox", &envelope.hash, "passed").unwrap();
+    let envelopes = mdir.get_envelopes("inbox", 1, 0).unwrap();
     let envelopes: &MaildirEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(!envelope.flags.contains(&MaildirFlag::Seen));
@@ -78,19 +81,19 @@ fn test_maildir_backend() {
     assert!(!envelope.flags.contains(&MaildirFlag::Passed));
 
     // check that the message can be copied
-    mdir.copy_msg("INBOX", "Subdir", &envelope.hash).unwrap();
-    assert!(mdir.get_msg("INBOX", &hash).is_ok());
-    assert!(mdir.get_msg("Subdir", &hash).is_ok());
-    assert!(mdir_subdir.get_msg("INBOX", &hash).is_ok());
+    mdir.copy_msg("inbox", "subdir", &envelope.hash).unwrap();
+    assert!(mdir.get_msg("inbox", &hash).is_ok());
+    assert!(mdir.get_msg("subdir", &hash).is_ok());
+    assert!(mdir_subdir.get_msg("inbox", &hash).is_ok());
 
     // check that the message can be moved
-    mdir.move_msg("INBOX", "Subdir", &envelope.hash).unwrap();
-    assert!(mdir.get_msg("INBOX", &hash).is_err());
-    assert!(mdir.get_msg("Subdir", &hash).is_ok());
-    assert!(mdir_subdir.get_msg("INBOX", &hash).is_ok());
+    mdir.move_msg("inbox", "subdir", &envelope.hash).unwrap();
+    assert!(mdir.get_msg("inbox", &hash).is_err());
+    assert!(mdir.get_msg("subdir", &hash).is_ok());
+    assert!(mdir_subdir.get_msg("inbox", &hash).is_ok());
 
     // check that the message can be deleted
-    mdir.del_msg("Subdir", &hash).unwrap();
-    assert!(mdir.get_msg("Subdir", &hash).is_err());
-    assert!(mdir_subdir.get_msg("INBOX", &hash).is_err());
+    mdir.del_msg("subdir", &hash).unwrap();
+    assert!(mdir.get_msg("subdir", &hash).is_err());
+    assert!(mdir_subdir.get_msg("inbox", &hash).is_err());
 }
diff --git a/tests/test_notmuch_backend.rs b/tests/test_notmuch_backend.rs
index d015073..93e707b 100644
--- a/tests/test_notmuch_backend.rs
+++ b/tests/test_notmuch_backend.rs
@@ -49,7 +49,7 @@ fn test_notmuch_backend() {
     notmuch
         .add_flags("", &envelope.hash, "flagged passed")
         .unwrap();
-    let envelopes = notmuch.get_envelopes("inbox", 1, 0).unwrap();
+    let envelopes = notmuch.get_envelopes("inbox", 10, 0).unwrap();
     let envelopes: &NotmuchEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(envelope.flags.contains(&"inbox".into()));
@@ -61,7 +61,7 @@ fn test_notmuch_backend() {
     notmuch
         .set_flags("", &envelope.hash, "inbox passed")
         .unwrap();
-    let envelopes = notmuch.get_envelopes("inbox", 1, 0).unwrap();
+    let envelopes = notmuch.get_envelopes("inbox", 10, 0).unwrap();
     let envelopes: &NotmuchEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(envelope.flags.contains(&"inbox".into()));
@@ -71,11 +71,15 @@ fn test_notmuch_backend() {
 
     // check that a flag can be removed from the message
     notmuch.del_flags("", &envelope.hash, "passed").unwrap();
-    let envelopes = notmuch.get_envelopes("inbox", 1, 0).unwrap();
+    let envelopes = notmuch.get_envelopes("inbox", 10, 0).unwrap();
     let envelopes: &NotmuchEnvelopes = envelopes.as_any().downcast_ref().unwrap();
     let envelope = envelopes.first().unwrap();
     assert!(envelope.flags.contains(&"inbox".into()));
     assert!(!envelope.flags.contains(&"seen".into()));
     assert!(!envelope.flags.contains(&"flagged".into()));
     assert!(!envelope.flags.contains(&"passed".into()));
+
+    // check that the message can be deleted
+    notmuch.del_msg("", &hash).unwrap();
+    assert!(notmuch.get_msg("inbox", &hash).is_err());
 }