diff --git a/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.cpp b/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.cpp
index 6d381434..784d45d8 100644
--- a/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.cpp
+++ b/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.cpp
@@ -43,6 +43,9 @@ SettingsTab::SettingsTab(QWidget *parent)
     connect(ui_.buttonInternetOn, &QPushButton::clicked, []() { app().grpc().sendEvent(newInternetStatusEvent(true)); });
     connect(ui_.buttonInternetOff, &QPushButton::clicked, []() { app().grpc().sendEvent(newInternetStatusEvent(false)); });
     connect(ui_.buttonShowMainWindow, &QPushButton::clicked, []() { app().grpc().sendEvent(newShowMainWindowEvent()); });
+    connect(ui_.buttonAPICertIssue, &QPushButton::clicked, []() {app().grpc().sendEvent(newApiCertIssueEvent()); });
+    connect(ui_.buttonNoActiveKeyForRecipient, &QPushButton::clicked, [&]() {app().grpc().sendEvent(
+        newNoActiveKeyForRecipientEvent(ui_.editNoActiveKeyForRecipient->text())); });
     connect(ui_.checkNextCacheChangeWillSucceed, &QCheckBox::toggled, this, &SettingsTab::updateGUIState);
     this->resetUI();
     this->updateGUIState();
diff --git a/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.ui b/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.ui
index d67c0671..3b45527b 100644
--- a/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.ui
+++ b/internal/frontend/bridge-gui/bridge-gui-tester/Tabs/SettingsTab.ui
@@ -703,19 +703,6 @@
               </property>
              </widget>
             </item>
-            <item>
-             <spacer name="horizontalSpacer_2">
-              <property name="orientation">
-               <enum>Qt::Horizontal</enum>
-              </property>
-              <property name="sizeHint" stdset="0">
-               <size>
-                <width>0</width>
-                <height>10</height>
-               </size>
-              </property>
-             </spacer>
-            </item>
             <item>
              <widget class="QPushButton" name="buttonInternetOn">
               <property name="text">
@@ -723,19 +710,6 @@
               </property>
              </widget>
             </item>
-            <item>
-             <spacer name="horizontalSpacer_4">
-              <property name="orientation">
-               <enum>Qt::Horizontal</enum>
-              </property>
-              <property name="sizeHint" stdset="0">
-               <size>
-                <width>0</width>
-                <height>10</height>
-               </size>
-              </property>
-             </spacer>
-            </item>
             <item>
              <widget class="QPushButton" name="buttonShowMainWindow">
               <property name="text">
@@ -743,6 +717,31 @@
               </property>
              </widget>
             </item>
+            <item>
+             <widget class="QPushButton" name="buttonAPICertIssue">
+              <property name="text">
+               <string>API cert. Issue</string>
+              </property>
+             </widget>
+            </item>
+           </layout>
+          </item>
+          <item>
+           <layout class="QHBoxLayout" name="horizontalLayout_12">
+            <item>
+             <widget class="QPushButton" name="buttonNoActiveKeyForRecipient">
+              <property name="text">
+               <string>No Active Key For Recipient</string>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <widget class="QLineEdit" name="editNoActiveKeyForRecipient">
+              <property name="text">
+               <string>dummy.user@proton.me</string>
+              </property>
+             </widget>
+            </item>
            </layout>
           </item>
           <item>
diff --git a/internal/frontend/bridge-gui/bridge-gui/qml/NotificationDialog.qml b/internal/frontend/bridge-gui/bridge-gui/qml/NotificationDialog.qml
index 3af8f070..e729e19f 100644
--- a/internal/frontend/bridge-gui/bridge-gui/qml/NotificationDialog.qml
+++ b/internal/frontend/bridge-gui/bridge-gui/qml/NotificationDialog.qml
@@ -68,6 +68,7 @@ Dialog {
 
         Label {
             Layout.alignment: Qt.AlignHCenter
+            horizontalAlignment: Text.AlignHCenter
             Layout.bottomMargin: 8
             colorScheme: root.colorScheme
             text: root.notification.title
diff --git a/internal/frontend/bridge-gui/bridge-gui/qml/NotificationPopups.qml b/internal/frontend/bridge-gui/bridge-gui/qml/NotificationPopups.qml
index 65f27b9d..f4aee23b 100644
--- a/internal/frontend/bridge-gui/bridge-gui/qml/NotificationPopups.qml
+++ b/internal/frontend/bridge-gui/bridge-gui/qml/NotificationPopups.qml
@@ -128,4 +128,14 @@ Item {
         colorScheme: root.colorScheme
         notification: root.notifications.rebuildKeychain
     }
+
+    NotificationDialog {
+        colorScheme: root.colorScheme
+        notification: root.notifications.apiCertIssue
+    }
+
+    NotificationDialog {
+        colorScheme: root.colorScheme
+        notification: root.notifications.noActiveKeyForRecipient
+    }
 }
diff --git a/internal/frontend/bridge-gui/bridge-gui/qml/Notifications/Notifications.qml b/internal/frontend/bridge-gui/bridge-gui/qml/Notifications/Notifications.qml
index d3204b9a..d638ac4c 100644
--- a/internal/frontend/bridge-gui/bridge-gui/qml/Notifications/Notifications.qml
+++ b/internal/frontend/bridge-gui/bridge-gui/qml/Notifications/Notifications.qml
@@ -77,7 +77,9 @@ QtObject {
         root.deleteAccount,
         root.noKeychain,
         root.rebuildKeychain,
-        root.addressChanged
+        root.addressChanged,
+        root.apiCertIssue,
+        root.noActiveKeyForRecipient
     ]
 
     // Connection
@@ -1051,4 +1053,63 @@ QtObject {
             }
         ]
     }
+
+    property Notification apiCertIssue: Notification {
+        title: qsTr("Unable to establish a \nsecure connection to \nProton servers")
+        description: qsTr("Bridge cannot verify the authenticity of Proton servers on your current network due to a TLS certificate error. " +
+            "Start Bridge again after ensuring your connection is secure and/or connecting to a VPN. Learn more about TLS pinning " +
+            "<a href=\"https://proton.me/blog/tls-ssl-certificate#Extra-security-precautions-taken-by-ProtonMail\">here</a>.")
+
+        brief: title
+        icon: "./icons/ic-exclamation-circle-filled.svg"
+        type: Notification.NotificationType.Danger
+        group: Notifications.Group.Dialogs | Notifications.Group.Connection
+
+        Connections {
+            target: Backend
+
+            function onApiCertIssue() {
+                root.apiCertIssue.active = true
+            }
+        }
+
+        action: [
+            Action {
+                text: qsTr("Quit Bridge")
+
+                onTriggered: {
+                    root.apiCertIssue.active = false;
+                    Backend.quit()
+                }
+            }
+        ]
+    }
+
+    property Notification noActiveKeyForRecipient: Notification {
+        title: qsTr("Unable to send \nencrypted message")
+        description: "#PlaceholderText#"
+        icon: "./icons/ic-exclamation-circle-filled.svg"
+        type: Notification.NotificationType.Danger
+        group: Notifications.Group.Dialogs | Notifications.Group.Connection
+
+        Connections {
+            target: Backend
+
+            function onNoActiveKeyForRecipient(email) {
+                root.noActiveKeyForRecipient.description = qsTr("There are no active keys to encrypt your message to %1. "+
+                    "Please update the setting for this contact.").arg(email)
+                root.noActiveKeyForRecipient.active = true
+            }
+        }
+
+        action: [
+            Action {
+                text: qsTr("OK")
+
+                onTriggered: {
+                    root.noActiveKeyForRecipient.active = false
+                }
+            }
+        ]
+    }
 }
diff --git a/internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.cpp b/internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.cpp
index 2178486e..54e96aea 100644
--- a/internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.cpp
+++ b/internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.cpp
@@ -1382,9 +1382,12 @@ void GRPCClient::processMailEvent(MailEvent const &event)
     switch (event.event_case())
     {
     case MailEvent::kNoActiveKeyForRecipientEvent:
-        this->logTrace("Mail event received: kNoActiveKeyForRecipientEvent.");
-        emit noActiveKeyForRecipient(QString::fromStdString(event.noactivekeyforrecipientevent().email()));
+    {
+        QString const email = QString::fromStdString(event.noactivekeyforrecipientevent().email());
+        this->logTrace(QString("Mail event received: NoActiveKeyForRecipient (email = %1).").arg(email));
+        emit noActiveKeyForRecipient(email);
         break;
+    }
     case MailEvent::kAddressChanged:
         this->logTrace("Mail event received: AddressChanged.");
         emit addressChanged(QString::fromStdString(event.addresschanged().address()));