diff --git a/server/src/jamid/jami-signal-interfaces.ts b/server/src/jamid/jami-signal-interfaces.ts
index 06dd6ed..a839309 100644
--- a/server/src/jamid/jami-signal-interfaces.ts
+++ b/server/src/jamid/jami-signal-interfaces.ts
@@ -59,7 +59,26 @@
 export interface IncomingAccountMessage {
   accountId: string;
   from: string;
-  message: Record<string, string>;
+  payload: Record<string, string>;
+}
+
+export interface AccountMessageStatusChanged {
+  accountId: string;
+  messageId: string;
+  peer: string;
+  state: number; // TODO: Replace state number with enum (see account_const.h)
+}
+
+export interface ContactAdded {
+  accountId: string;
+  contactId: string;
+  confirmed: boolean;
+}
+
+export interface ContactRemoved {
+  accountId: string;
+  contactId: string;
+  banned: boolean;
 }
 
 export interface ConversationReady {
diff --git a/server/src/jamid/jamid.ts b/server/src/jamid/jamid.ts
index 283e527..a3db747 100644
--- a/server/src/jamid/jamid.ts
+++ b/server/src/jamid/jamid.ts
@@ -24,6 +24,9 @@
 import { JamiSignal } from './jami-signal.js';
 import {
   AccountDetailsChanged,
+  AccountMessageStatusChanged,
+  ContactAdded,
+  ContactRemoved,
   ConversationLoaded,
   ConversationReady,
   ConversationRemoved,
@@ -93,8 +96,20 @@
       onKnownDevicesChanged.next({ accountId, devices });
 
     const onIncomingAccountMessage = new Subject<IncomingAccountMessage>();
-    handlers.IncomingAccountMessage = (accountId: string, from: string, message: Record<string, string>) =>
-      onIncomingAccountMessage.next({ accountId, from, message });
+    handlers.IncomingAccountMessage = (accountId: string, from: string, payload: Record<string, string>) =>
+      onIncomingAccountMessage.next({ accountId, from, payload });
+
+    const onAccountMessageStatusChanged = new Subject<AccountMessageStatusChanged>();
+    handlers.AccountMessageStatusChanged = (accountId: string, messageId: string, peer: string, state: number) =>
+      onAccountMessageStatusChanged.next({ accountId, messageId, peer, state });
+
+    const onContactAdded = new Subject<ContactAdded>();
+    handlers.ContactAdded = (accountId: string, contactId: string, confirmed: boolean) =>
+      onContactAdded.next({ accountId, contactId, confirmed });
+
+    const onContactRemoved = new Subject<ContactRemoved>();
+    handlers.ContactRemoved = (accountId: string, contactId: string, banned: boolean) =>
+      onContactRemoved.next({ accountId, contactId, banned });
 
     const onConversationReady = new Subject<ConversationReady>();
     handlers.ConversationReady = (accountId: string, conversationId: string) =>
@@ -122,6 +137,9 @@
       onRegisteredNameFound: onRegisteredNameFound.asObservable(),
       onKnownDevicesChanged: onKnownDevicesChanged.asObservable(),
       onIncomingAccountMessage: onIncomingAccountMessage.asObservable(),
+      onAccountMessageStatusChanged: onAccountMessageStatusChanged.asObservable(),
+      onContactAdded: onContactAdded.asObservable(),
+      onContactRemoved: onContactRemoved.asObservable(),
       onConversationReady: onConversationReady.asObservable(),
       onConversationRemoved: onConversationRemoved.asObservable(),
       onConversationLoaded: onConversationLoaded.asObservable(),
@@ -351,7 +369,7 @@
 
     this.events.onIncomingAccountMessage.subscribe((signal) => {
       log.debug('Received IncomingAccountMessage:', JSON.stringify(signal));
-      const message = JSON.parse(signal.message['application/json']);
+      const message = JSON.parse(signal.payload['application/json']);
 
       if (message === undefined) {
         log.debug('Undefined account message');
@@ -369,6 +387,18 @@
       this.ws.send(signal.accountId, message);
     });
 
+    this.events.onAccountMessageStatusChanged.subscribe((signal) => {
+      log.debug('Received AccountMessageStatusChanged:', JSON.stringify(signal));
+    });
+
+    this.events.onContactAdded.subscribe((signal) => {
+      log.debug('Received ContactAdded:', JSON.stringify(signal));
+    });
+
+    this.events.onContactRemoved.subscribe((signal) => {
+      log.debug('Received ContactRemoved:', JSON.stringify(signal));
+    });
+
     this.events.onConversationReady.subscribe((signal) => {
       log.debug('Received ConversationReady:', JSON.stringify(signal));
     });
diff --git a/server/src/middleware/auth.ts b/server/src/middleware/auth.ts
index 715db0a..4f06992 100644
--- a/server/src/middleware/auth.ts
+++ b/server/src/middleware/auth.ts
@@ -52,7 +52,7 @@
       res.locals.accountId = payload.id;
       next();
     } catch (e) {
-      res.sendStatus(HttpStatusCode.Unauthorized);
+      res.status(HttpStatusCode.Unauthorized).send('Invalid access token');
     }
   };
 }
diff --git a/server/src/middleware/setup.ts b/server/src/middleware/setup.ts
index 3575fd0..a697b5a 100644
--- a/server/src/middleware/setup.ts
+++ b/server/src/middleware/setup.ts
@@ -27,8 +27,9 @@
   const isSetupComplete = adminConfig.get() !== undefined;
 
   if (!isSetupComplete) {
-    res.sendStatus(HttpStatusCode.Forbidden);
+    res.status(HttpStatusCode.Forbidden).send('Setup not complete');
     return;
   }
+
   next();
 }
diff --git a/server/src/routers/account-router.ts b/server/src/routers/account-router.ts
index 7bccea7..4e1722d 100644
--- a/server/src/routers/account-router.ts
+++ b/server/src/routers/account-router.ts
@@ -30,9 +30,6 @@
 
 accountRouter.use(authenticateToken);
 
-// TODO: If tokens can be generated on one daemon and used on another (transferrable between daemons),
-// then add middleware to check that the currently logged-in accountId is stored in this daemon instance
-
 // TODO: Do we really need this route to return the default moderators?
 // It would be cleaner just to GET /default-moderators for this
 accountRouter.get(
@@ -51,7 +48,7 @@
       });
     }
 
-    res.json({
+    res.send({
       id: accountId,
       details: jamid.getAccountDetails(accountId),
       volatileDetails: jamid.getVolatileAccountDetails(accountId),
@@ -63,18 +60,22 @@
 
 accountRouter.patch('/', (req, res) => {
   const accountId = res.locals.accountId;
+
   const currentAccountDetails = jamid.getAccountDetails(accountId);
   const newAccountDetails: AccountDetails = { ...currentAccountDetails, ...req.body };
   jamid.setAccountDetails(accountId, newAccountDetails);
+
   res.sendStatus(HttpStatusCode.NoContent);
 });
 
+// TODO: Should this endpoint be removed?
 accountRouter.post('/send-account-message', (req: Request<ParamsDictionary, any, AccountTextMessage>, res) => {
   const { from, to, message } = req.body;
-  if (!from || !to || !message) {
-    res.status(HttpStatusCode.BadRequest).send('Missing arguments in request');
+  if (from === undefined || to === undefined || message === undefined) {
+    res.status(HttpStatusCode.BadRequest).send('Missing from, to, or message in body');
     return;
   }
+
   jamid.sendAccountTextMessage(from, to, JSON.stringify(message));
-  res.end();
+  res.sendStatus(HttpStatusCode.NoContent);
 });
diff --git a/server/src/routers/auth-router.ts b/server/src/routers/auth-router.ts
index 086f640..f04529e 100644
--- a/server/src/routers/auth-router.ts
+++ b/server/src/routers/auth-router.ts
@@ -42,8 +42,13 @@
   '/new-account',
   asyncHandler(async (req: Request<ParamsDictionary, string, Credentials>, res, _next) => {
     const { username, password } = req.body;
-    if (!username || !password) {
-      res.status(HttpStatusCode.BadRequest).send('Missing username or password');
+    if (username === undefined || password === undefined) {
+      res.status(HttpStatusCode.BadRequest).send('Missing username or password in body');
+      return;
+    }
+
+    if (password === '') {
+      res.status(HttpStatusCode.BadRequest).send('Password may not be empty');
       return;
     }
 
@@ -82,8 +87,8 @@
   '/login',
   asyncHandler(async (req: Request<ParamsDictionary, { accessToken: string } | string, Credentials>, res, _next) => {
     const { username, password } = req.body;
-    if (!username || !password) {
-      res.status(HttpStatusCode.BadRequest).send('Missing username or password');
+    if (username === undefined || password === undefined) {
+      res.status(HttpStatusCode.BadRequest).send('Missing username or password in body');
       return;
     }
 
@@ -99,13 +104,15 @@
     // TODO: load the password from Jami
     const hashedPassword = creds.get(username);
     if (!hashedPassword) {
-      res.status(HttpStatusCode.NotFound).send('Password not found');
+      res
+        .status(HttpStatusCode.NotFound)
+        .send('Password not found (the account does not have a password set on the server)');
       return;
     }
 
     const isPasswordVerified = await argon2.verify(hashedPassword, password);
     if (!isPasswordVerified) {
-      res.sendStatus(HttpStatusCode.Unauthorized);
+      res.status(HttpStatusCode.Unauthorized).send('Incorrect password');
       return;
     }
 
diff --git a/server/src/routers/call-router.ts b/server/src/routers/call-router.ts
index 835bf66..96cd7ce 100644
--- a/server/src/routers/call-router.ts
+++ b/server/src/routers/call-router.ts
@@ -16,6 +16,7 @@
  * <https://www.gnu.org/licenses/>.
  */
 import { Router } from 'express';
+import { HttpStatusCode } from 'jami-web-common';
 import { Container } from 'typedi';
 
 import { Jamid } from '../jamid/jamid.js';
@@ -34,5 +35,11 @@
 
 callRouter.get('/:callId', (req, res) => {
   const callDetails = jamid.getCallDetails(res.locals.accountId, req.params.callId);
+
+  if (Object.keys(callDetails).length === 0) {
+    res.status(HttpStatusCode.NotFound).send('No such call found');
+    return;
+  }
+
   res.send(callDetails);
 });
diff --git a/server/src/routers/contacts-router.ts b/server/src/routers/contacts-router.ts
index 8d51d2b..d757d52 100644
--- a/server/src/routers/contacts-router.ts
+++ b/server/src/routers/contacts-router.ts
@@ -35,6 +35,12 @@
 
 contactsRouter.get('/:contactId', (req, res) => {
   const contactDetails = jamid.getContactDetails(res.locals.accountId, req.params.contactId);
+
+  if (Object.keys(contactDetails).length === 0) {
+    res.status(HttpStatusCode.NotFound).send('No such contact found');
+    return;
+  }
+
   res.send(contactDetails);
 });
 
@@ -45,6 +51,11 @@
   jamid.addContact(accountId, contactId);
 
   const contactDetails = jamid.getContactDetails(accountId, contactId);
+  if (Object.keys(contactDetails).length === 0) {
+    res.status(HttpStatusCode.NotFound).send('No such contact found');
+    return;
+  }
+
   res.send(contactDetails);
 });
 
diff --git a/server/src/routers/conversation-router.ts b/server/src/routers/conversation-router.ts
index 164ea3e..224962c 100644
--- a/server/src/routers/conversation-router.ts
+++ b/server/src/routers/conversation-router.ts
@@ -37,6 +37,10 @@
 // TODO: Create interface for return type in common/ when Records and interfaces are refactored
 async function createConversationResponseObject(accountId: string, accountUri: string, conversationId: string) {
   const infos = jamid.getConversationInfos(accountId, conversationId);
+  if (Object.keys(infos).length === 0) {
+    return undefined;
+  }
+
   const members = jamid.getConversationMembers(accountId, conversationId);
 
   const namedMembers = [];
@@ -94,21 +98,29 @@
   })
 );
 
-conversationRouter.post('/', (req: Request<ParamsDictionary, Record<string, string>, ConversationMembers>, res) => {
-  const accountId = res.locals.accountId;
+conversationRouter.post(
+  '/',
+  (req: Request<ParamsDictionary, Record<string, string> | string, ConversationMembers>, res) => {
+    const { members } = req.body;
+    if (members === undefined || members.length !== 1) {
+      res.status(HttpStatusCode.BadRequest).send('Missing members or more than one member in body');
+      return;
+    }
 
-  const { members } = req.body;
-  if (members === undefined || members.length !== 1) {
-    res.sendStatus(HttpStatusCode.BadRequest);
-    return;
+    const accountId = res.locals.accountId;
+
+    const contactId = members[0];
+    jamid.addContact(accountId, contactId);
+
+    const contactDetails = jamid.getContactDetails(accountId, contactId);
+    if (Object.keys(contactDetails).length === 0) {
+      res.status(HttpStatusCode.NotFound).send('No such member found');
+      return;
+    }
+
+    res.send(contactDetails);
   }
-
-  const contactId = members[0];
-  jamid.addContact(accountId, contactId);
-
-  const contactDetails = jamid.getContactDetails(accountId, contactId);
-  res.send(contactDetails);
-});
+);
 
 // TODO: Check if we actually need this endpoint to return messages.
 // Verify by checking what is truly needed in the client when migrating, to clean up the API.
@@ -124,13 +136,12 @@
     // Retrieve the URI of the current account (Account.username actually stores the URI rather than the username)
     const accountUri = jamid.getAccountDetails(accountId)['Account.username'];
 
-    const conversationIds = jamid.getConversationIds(accountId);
-    if (!conversationIds.includes(conversationId)) {
-      res.sendStatus(HttpStatusCode.NotFound);
+    const conversation = await createConversationResponseObject(accountId, accountUri, conversationId);
+    if (conversation === undefined) {
+      res.status(HttpStatusCode.NotFound).send('No such conversation found');
       return;
     }
 
-    const conversation = await createConversationResponseObject(accountId, accountUri, conversationId);
     res.send(conversation);
   })
 );
@@ -141,9 +152,9 @@
     const accountId = res.locals.accountId;
     const conversationId = req.params.conversationId;
 
-    const conversationIds = jamid.getConversationIds(accountId);
-    if (!conversationIds.includes(conversationId)) {
-      res.sendStatus(HttpStatusCode.NotFound);
+    const infos = jamid.getConversationInfos(accountId, conversationId);
+    if (Object.keys(infos).length === 0) {
+      res.status(HttpStatusCode.NotFound).send('No such conversation found');
       return;
     }
 
@@ -157,11 +168,20 @@
   (req: Request<ParamsDictionary, any, ConversationMessage>, res) => {
     const { message } = req.body;
     if (message === undefined) {
-      res.sendStatus(HttpStatusCode.BadRequest);
+      res.status(HttpStatusCode.BadRequest).send('Missing message in body');
       return;
     }
 
-    jamid.sendConversationMessage(res.locals.accountId, req.params.conversationId, message);
-    res.end();
+    const accountId = res.locals.accountId;
+    const conversationId = req.params.conversationId;
+
+    const infos = jamid.getConversationInfos(accountId, conversationId);
+    if (Object.keys(infos).length === 0) {
+      res.status(HttpStatusCode.NotFound).send('No such conversation found');
+      return;
+    }
+
+    jamid.sendConversationMessage(accountId, conversationId, message);
+    res.sendStatus(HttpStatusCode.NoContent);
   }
 );
diff --git a/server/src/routers/default-moderators-router.ts b/server/src/routers/default-moderators-router.ts
index 797aac3..06d79ca 100644
--- a/server/src/routers/default-moderators-router.ts
+++ b/server/src/routers/default-moderators-router.ts
@@ -51,7 +51,7 @@
 
 defaultModeratorsRouter.put('/:contactId', (req, res) => {
   jamid.addDefaultModerator(res.locals.accountId, req.params.contactId);
-  res.end();
+  res.sendStatus(HttpStatusCode.NoContent);
 });
 
 defaultModeratorsRouter.delete('/:contactId', (req, res) => {
diff --git a/server/src/routers/nameserver-router.ts b/server/src/routers/nameserver-router.ts
index 6e49b52..2ead8ee 100644
--- a/server/src/routers/nameserver-router.ts
+++ b/server/src/routers/nameserver-router.ts
@@ -35,13 +35,13 @@
     const result = await jamid.lookupUsername(req.params.username, res.locals.accountId);
     switch (result.state) {
       case 0:
-        res.json(result);
+        res.send(result);
         break;
       case 1:
-        res.sendStatus(HttpStatusCode.BadRequest);
+        res.status(HttpStatusCode.BadRequest).send('Invalid username');
         break;
       default:
-        res.sendStatus(HttpStatusCode.NotFound);
+        res.status(HttpStatusCode.NotFound).send('No such username found');
         break;
     }
   })
@@ -53,13 +53,13 @@
     const result = await jamid.lookupAddress(req.params.address, res.locals.accountId);
     switch (result.state) {
       case 0:
-        res.json(result);
+        res.send(result);
         break;
       case 1:
-        res.sendStatus(HttpStatusCode.BadRequest);
+        res.status(HttpStatusCode.BadRequest).send('Invalid address');
         break;
       default:
-        res.sendStatus(HttpStatusCode.NotFound);
+        res.status(HttpStatusCode.NotFound).send('No such address found');
         break;
     }
   })
diff --git a/server/src/routers/setup-router.ts b/server/src/routers/setup-router.ts
index d155ef5..7dfa24f 100644
--- a/server/src/routers/setup-router.ts
+++ b/server/src/routers/setup-router.ts
@@ -40,19 +40,25 @@
 setupRouter.post(
   '/admin/create',
   asyncHandler(async (req: Request<ParamsDictionary, string, { password?: string }>, res, _next) => {
-    const isAdminCreated = adminConfig.get() !== undefined;
-    if (isAdminCreated) {
-      res.sendStatus(HttpStatusCode.BadRequest);
+    const { password } = req.body;
+    if (password === undefined) {
+      res.status(HttpStatusCode.BadRequest).send('Missing password in body');
       return;
     }
 
-    const { password } = req.body;
-    if (!password) {
-      res.status(HttpStatusCode.BadRequest).send('Missing password');
+    if (password === '') {
+      res.status(HttpStatusCode.BadRequest).send('Password may not be empty');
+      return;
+    }
+
+    const isAdminCreated = adminConfig.get() !== undefined;
+    if (isAdminCreated) {
+      res.status(HttpStatusCode.Conflict).send('Admin already exists');
       return;
     }
 
     const hashedPassword = await argon2.hash(password, { type: argon2.argon2id });
+
     adminConfig.set(hashedPassword);
     await adminConfig.save();
 
@@ -62,7 +68,7 @@
 
 // Every request handler after this line will be submitted to this middleware
 // in order to ensure that the admin account is set up before proceeding with
-// setup related requests.
+// setup related requests
 setupRouter.use(checkAdminSetup);
 
 setupRouter.post(
@@ -70,15 +76,16 @@
   asyncHandler(
     async (req: Request<ParamsDictionary, { accessToken: string } | string, { password: string }>, res, _next) => {
       const { password } = req.body;
-      if (!password) {
-        res.status(HttpStatusCode.BadRequest).send('Missing password');
+      if (password === undefined) {
+        res.status(HttpStatusCode.BadRequest).send('Missing password in body');
         return;
       }
 
       const hashedPassword = adminConfig.get();
+
       const isPasswordVerified = await argon2.verify(hashedPassword, password);
       if (!isPasswordVerified) {
-        res.sendStatus(HttpStatusCode.Forbidden);
+        res.status(HttpStatusCode.Forbidden).send('Incorrect password');
         return;
       }