diff --git a/calendar/base/content/dialogs/calendar-event-dialog-reminder.js b/calendar/base/content/dialogs/calendar-event-dialog-reminder.js
index b12839b667..36667386eb 100644
--- a/calendar/base/content/dialogs/calendar-event-dialog-reminder.js
+++ b/calendar/base/content/dialogs/calendar-event-dialog-reminder.js
@@ -192,13 +192,7 @@ function setupMaxReminders() {
       null,
       gReminderNotification.PRIORITY_WARNING_MEDIUM
     );
-
-    if (gReminderNotification.gProton) {
-      notification.closeButton.hidden = true;
-    } else {
-      let closeButton = notification.messageDetails.nextElementSibling;
-      closeButton.setAttribute("hidden", "true");
-    }
+    notification.closeButton.hidden = true;
   } else {
     gReminderNotification.removeAllNotifications();
   }
diff --git a/mail/base/content/mailWindowOverlay.js b/mail/base/content/mailWindowOverlay.js
index 0da30b7642..faac5789db 100644
--- a/mail/base/content/mailWindowOverlay.js
+++ b/mail/base/content/mailWindowOverlay.js
@@ -3351,16 +3351,9 @@ var gMessageNotificationBar = {
         aCanOverride ? buttons : []
       );
 
-      // Update the button differently based on the Proton pref.
-      if (this.msgNotificationBar.gProton) {
-        notification.buttonContainer.firstElementChild.classList.add(
-          "button-menu-list"
-        );
-        return;
-      }
-
-      let button = notification.spacer.nextElementSibling;
-      button.classList.add("button-menu-list");
+      notification.buttonContainer.firstElementChild.classList.add(
+        "button-menu-list"
+      );
     }
   },
 
@@ -3400,16 +3393,9 @@ var gMessageNotificationBar = {
         buttons
       );
 
-      // Update the button differently based on the Proton pref.
-      if (this.msgNotificationBar.gProton) {
-        notification.buttonContainer.firstElementChild.classList.add(
-          "button-menu-list"
-        );
-        return;
-      }
-
-      let button = notification.spacer.nextElementSibling;
-      button.classList.add("button-menu-list");
+      notification.buttonContainer.firstElementChild.classList.add(
+        "button-menu-list"
+      );
     }
   },
 
diff --git a/mail/components/accountcreation/content/accountSetup.js b/mail/components/accountcreation/content/accountSetup.js
index 3062b48b31..a1ff897cda 100644
--- a/mail/components/accountcreation/content/accountSetup.js
+++ b/mail/components/accountcreation/content/accountSetup.js
@@ -792,12 +792,7 @@ var gAccountSetup = {
     notification.setAttribute("align", "center");
 
     // Hide the close button to prevent dismissing the notification.
-    if (this.notificationBox.gProton) {
-      notification.removeAttribute("dismissable");
-    } else {
-      let closeButton = notification.messageDetails.nextElementSibling;
-      closeButton.hidden = true;
-    }
+    notification.removeAttribute("dismissable");
 
     this.ensureVisibleNotification();
   },
@@ -839,12 +834,7 @@ var gAccountSetup = {
     notification.setAttribute("type", "success");
 
     // Hide the close button to prevent dismissing the notification.
-    if (this.notificationBox.gProton) {
-      notification.removeAttribute("dismissable");
-    } else {
-      let closeButton = notification.messageDetails.nextElementSibling;
-      closeButton.hidden = true;
-    }
+    notification.removeAttribute("dismissable");
 
     this.showHelperImage("step3");
 
@@ -891,12 +881,7 @@ var gAccountSetup = {
     );
 
     // Hide the close button to prevent dismissing the notification.
-    if (this.notificationBox.gProton) {
-      notification.removeAttribute("dismissable");
-    } else {
-      let closeButton = notification.messageDetails.nextElementSibling;
-      closeButton.hidden = true;
-    }
+    notification.removeAttribute("dismissable");
 
     this.ensureVisibleNotification();
   },
@@ -1900,12 +1885,7 @@ var gAccountSetup = {
       );
 
       // Hide the close button to prevent dismissing the notification.
-      if (this.notificationBox.gProton) {
-        notification.removeAttribute("dismissable");
-      } else {
-        let closeButton = notification.messageDetails.nextElementSibling;
-        closeButton.hidden = true;
-      }
+      notification.removeAttribute("dismissable");
     }
   },
 
diff --git a/mail/components/compose/content/MsgComposeCommands.js b/mail/components/compose/content/MsgComposeCommands.js
index 4a0ed7fa76..c29de37fbb 100644
--- a/mail/components/compose/content/MsgComposeCommands.js
+++ b/mail/components/compose/content/MsgComposeCommands.js
@@ -2841,13 +2841,13 @@ function manageAttachmentNotification(aForce = false) {
   // specific keywords to the existing notification instead of creating it
   // from scratch.
   if (notification) {
-    let selector = this.gComposeNotification.gProton
-      ? notification.messageText
-      : notification;
-
-    let msgContainer = selector.querySelector("#attachmentReminderText");
+    let msgContainer = notification.messageText.querySelector(
+      "#attachmentReminderText"
+    );
     msgContainer.setAttribute("value", textValue);
-    let keywordsContainer = selector.querySelector("#attachmentKeywords");
+    let keywordsContainer = notification.messageText.querySelector(
+      "#attachmentKeywords"
+    );
     keywordsContainer.setAttribute("value", keywords);
     return;
   }
@@ -2913,19 +2913,10 @@ function manageAttachmentNotification(aForce = false) {
   );
   notification.setAttribute("id", "attachmentNotificationBox");
 
-  // Variation for Proton UI.
-  if (this.gComposeNotification.gProton) {
-    notification.messageText.appendChild(msg);
-    notification.buttonContainer.lastElementChild.appendChild(
-      remindLaterMenuPopup
-    );
-    return;
-  }
-
-  notification.messageDetails.querySelector("button").before(msg);
-  notification.messageDetails
-    .querySelector("button:last-child")
-    .appendChild(remindLaterMenuPopup);
+  notification.messageText.appendChild(msg);
+  notification.buttonContainer.lastElementChild.appendChild(
+    remindLaterMenuPopup
+  );
 }
 
 /**
@@ -5148,10 +5139,9 @@ function checkPublicRecipientsLimit() {
 
   // Reuse the existing notification since one is shown already.
   if (notification) {
-    let root = this.gComposeNotification.gProton
-      ? notification.messageText
-      : notification;
-    let msgText = root.querySelector(".consider-bcc-notification-text");
+    let msgText = notification.messageText.querySelector(
+      ".consider-bcc-notification-text"
+    );
     msgText.setAttribute(
       "data-l10n-args",
       JSON.stringify({ count: publicAddressPillsCount })
@@ -5211,17 +5201,7 @@ function checkPublicRecipientsLimit() {
     }
   );
   notification.setAttribute("id", "warnPublicRecipientsNotification");
-  // Variation for Proton UI.
-  if (this.gComposeNotification.gProton) {
-    notification.messageText.appendChild(msgText);
-    return;
-  }
-
-  // Ugh, the following isn't perfect... but !gProton may be dropped soon.
-  let msg = document.createElement("div");
-  msg.appendChild(msgText);
-  notification.messageDetails.style.display = "flex";
-  notification.messageDetails.querySelector("button").before(msg);
+  notification.messageText.appendChild(msgText);
 }
 
 /**