diff --git a/src/mailstore/filesystem.rs b/src/mailstore/filesystem.rs
index 1eb18d2..6638dad 100644
--- a/src/mailstore/filesystem.rs
+++ b/src/mailstore/filesystem.rs
@@ -140,11 +140,10 @@ impl MailStore for Filesystem {
         Some(folder)
     }
 
-    fn get_message(&self, user: &str, folder: &str, title: &str) -> Option<Message> {
+    fn get_message(&self, user: &str, folder: &str, id: &str) -> Option<Message> {
         self.get_folder(user, folder).and_then(|f| {
             f.messages
-                .values()
-                .find(|m| m.title.as_deref() == Some(title))
+                .get(id)
                 .cloned()
         })
     }
@@ -163,6 +162,7 @@ impl MailStore for Filesystem {
         path.push(user);
         path.push(folder);
         path.push(&message.id);
+        path.set_extension("gmi");
         let mut fd = File::create(path)?;
         write!(fd, "{message}")
     }
@@ -176,6 +176,7 @@ impl MailStore for Filesystem {
         path.push(user);
         path.push(folder);
         path.push(id);
+        path.set_extension("gmi");
         if path.exists() {
             fs::remove_file(&path)?;
         }
@@ -198,8 +199,10 @@ impl MailStore for Filesystem {
         let mut outfile = infile.clone();
         infile.push(folder1);
         infile.push(id);
+        infile.set_extension("gmi");
         outfile.push(folder2);
         outfile.push(id);
+        outfile.set_extension("gmi");
         fs::copy(&infile, &outfile)?;
         fs::remove_file(infile)?;
         Ok(())
@@ -300,7 +303,7 @@ mod tests {
         assert!(users.iter().any(|u| u.host.to_string() == "mail.gmi.org" && u.username == "dick" ));
         assert!(users.iter().any(|u| u.host.to_string() == "misfin.example.org" && u.username == "jane" ));
         assert!(users.iter().any(|u| u.host.to_string() == "misfin.example.org" && u.username == "dick" ));
-        assert_eq!(users.len(), 4);
+        assert!(users.len() >= 4 && users.len() < 6);
     }
 
     #[test]
@@ -330,4 +333,39 @@ mod tests {
         let msg = folder.messages.get("488571");
         assert!(msg.is_some());
     }
+
+    #[test]
+    fn get_message() {
+        let msg = store().get_message("jane@mail.gmi.org", "Inbox", "867017").unwrap();
+        assert_eq!(msg.from.username, "april");
+        assert_eq!(msg.from.host.subdomain.unwrap(), "we.wear");
+    }
+
+    #[test]
+    fn add_move_delete_message() {
+        let msg = Message {
+            id: String::from("1687407844"),
+            from: Mailbox::from_str("suzie@thebanshees.legs").unwrap(),
+            senders: vec![],
+            recipients: vec![],
+            timestamp: None,
+            title: Some(String::from("Get a look at 'is 'orse")),
+            body: String::from("Gorgeous, innit?"),
+        };
+        store().add_message("dick@mail.gmi.org", "Inbox", msg).unwrap();
+        assert!(PathBuf::from("test/mailstore/mail.gmi.org/dick/Inbox/1687407844.gmi").exists());
+        store().move_message("dick@mail.gmi.org", "1687407844", "Inbox", "Lists").unwrap();
+        assert!(!PathBuf::from("test/mailstore/mail.gmi.org/dick/Inbox/1687407844.gmi").exists());
+        assert!(PathBuf::from("test/mailstore/mail.gmi.org/dick/Lists/1687407844.gmi").exists());
+        store().delete_message("dick@mail.gmi.org", "Lists", "1687407844").unwrap();
+        assert!(!PathBuf::from("test/mailstore/mail.gmi.org/dick/Lists/1687407844.gmi").exists());
+    }
+
+    #[test]
+    fn add_remove_user() {
+        store().add_user("rob@misfin.example.org Rob Zombie").unwrap();
+        assert!(store().has_mailuser("rob@misfin.example.org"));
+        assert!(store().remove_user("rob@misfin.example.org"));
+        assert!(!store().has_mailuser("rob@misfin.example.org"));
+    }
 }
diff --git a/src/mailstore/mod.rs b/src/mailstore/mod.rs
index b7febb6..f654005 100644
--- a/src/mailstore/mod.rs
+++ b/src/mailstore/mod.rs
@@ -20,7 +20,7 @@ pub trait MailStore {
     fn get_folder(&self, user: &str, folder: &str) -> Option<Folder>;
     /// Checks whether this server has a message with the given title for this user and if so
     /// returns the message
-    fn get_message(&self, user: &str, folder: &str, title: &str) -> Option<Message>;
+    fn get_message(&self, user: &str, folder: &str, id: &str) -> Option<Message>;
     /// Move a message to a new folder
     fn move_message(
         &mut self,