diff --git a/dev/App/User.js b/dev/App/User.js
index 8c613e169..4cb1499ca 100644
--- a/dev/App/User.js
+++ b/dev/App/User.js
@@ -105,10 +105,10 @@ export class AppUser extends AbstractApp {
 	/**
 	 * @param {number} iFolderType
 	 * @param {string} sFromFolderFullName
-	 * @param {Array} aUidForRemove
+	 * @param {Set} oUids
 	 * @param {boolean=} bDelete = false
 	 */
-	moveMessagesToFolderType(iFolderType, sFromFolderFullName, aUidForRemove, bDelete) {
+	moveMessagesToFolderType(iFolderType, sFromFolderFullName, oUids, bDelete) {
 		let oMoveFolder = null,
 			nSetSystemFoldersNotification = null;
 
@@ -150,13 +150,13 @@ export class AppUser extends AbstractApp {
 			showScreenPopup(AskPopupView, [
 				i18n('POPUPS_ASK/DESC_WANT_DELETE_MESSAGES'),
 				() => {
-					messagesDeleteHelper(sFromFolderFullName, aUidForRemove);
-					MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, aUidForRemove);
+					messagesDeleteHelper(sFromFolderFullName, oUids);
+					MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, oUids);
 				}
 			]);
 		} else if (oMoveFolder) {
-			messagesMoveHelper(sFromFolderFullName, oMoveFolder.fullName, aUidForRemove);
-			MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, aUidForRemove, oMoveFolder.fullName);
+			messagesMoveHelper(sFromFolderFullName, oMoveFolder.fullName, oUids);
+			MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, oUids, oMoveFolder.fullName);
 		}
 	}
 
diff --git a/dev/Common/Folders.js b/dev/Common/Folders.js
index 86f77451b..075b41324 100644
--- a/dev/Common/Folders.js
+++ b/dev/Common/Folders.js
@@ -254,7 +254,7 @@ messagesMoveHelper = (fromFolderFullName, toFolderFullName, uidsForMove) => {
 		{
 			FromFolder: fromFolderFullName,
 			ToFolder: toFolderFullName,
-			Uids: uidsForMove.join(','),
+			Uids: [...uidsForMove].join(','),
 			MarkAsRead: (isSpam || FolderUserStore.trashFolder() === toFolderFullName) ? 1 : 0,
 			Learning: isSpam ? 'SPAM' : isHam ? 'HAM' : ''
 		}
@@ -266,19 +266,19 @@ messagesDeleteHelper = (sFromFolderFullName, aUidForRemove) => {
 		moveOrDeleteResponseHelper,
 		{
 			Folder: sFromFolderFullName,
-			Uids: aUidForRemove.join(',')
+			Uids: [...aUidForRemove].join(',')
 		}
 	);
 },
 
 /**
  * @param {string} sFromFolderFullName
- * @param {Array} aUidForMove
+ * @param {Set} oUids
  * @param {string} sToFolderFullName
  * @param {boolean=} bCopy = false
  */
-moveMessagesToFolder = (sFromFolderFullName, aUidForMove, sToFolderFullName, bCopy) => {
-	if (sFromFolderFullName !== sToFolderFullName && arrayLength(aUidForMove)) {
+moveMessagesToFolder = (sFromFolderFullName, oUids, sToFolderFullName, bCopy) => {
+	if (sFromFolderFullName !== sToFolderFullName && oUids?.size) {
 		const oFromFolder = getFolderFromCacheList(sFromFolderFullName),
 			oToFolder = getFolderFromCacheList(sToFolderFullName);
 
@@ -287,13 +287,13 @@ moveMessagesToFolder = (sFromFolderFullName, aUidForMove, sToFolderFullName, bCo
 				Remote.request('MessageCopy', null, {
 					FromFolder: oFromFolder.fullName,
 					ToFolder: oToFolder.fullName,
-					Uids: aUidForMove.join(',')
+					Uids: [...oUids].join(',')
 				});
 			} else {
-				messagesMoveHelper(oFromFolder.fullName, oToFolder.fullName, aUidForMove);
+				messagesMoveHelper(oFromFolder.fullName, oToFolder.fullName, oUids);
 			}
 
-			MessagelistUserStore.removeMessagesFromList(oFromFolder.fullName, aUidForMove, oToFolder.fullName, bCopy);
+			MessagelistUserStore.removeMessagesFromList(oFromFolder.fullName, oUids, oToFolder.fullName, bCopy);
 			return true;
 		}
 	}
diff --git a/dev/External/User/ko.js b/dev/External/User/ko.js
index 56d2d770f..3917b37a0 100644
--- a/dev/External/User/ko.js
+++ b/dev/External/User/ko.js
@@ -3,7 +3,6 @@ import ko from 'ko';
 import { HtmlEditor } from 'Common/Html';
 import { timeToNode } from 'Common/Translator';
 import { elementById, addEventsListeners, dropdowns } from 'Common/Globals';
-import { isArray } from 'Common/Utils';
 import { dropdownsDetectVisibility } from 'Common/UtilsUser';
 import { EmailAddressesComponent } from 'Component/EmailAddresses';
 import { ThemeStore } from 'Stores/Theme';
@@ -97,7 +96,7 @@ Object.assign(ko.bindingHandlers, {
 				let data = fValueAccessor()(e);
 				dragImage || (dragImage = elementById('messagesDragImage'));
 				if (data && dragImage && !ThemeStore.isMobile()) {
-					dragImage.querySelector('.text').textContent = data.uids.length;
+					dragImage.querySelector('.text').textContent = data.size;
 					let img = dragImage.querySelector('i');
 					img.classList.toggle('icon-copy', e.ctrlKey);
 					img.classList.toggle('icon-mail', !e.ctrlKey);
@@ -107,7 +106,7 @@ Object.assign(ko.bindingHandlers, {
 					dragImage.style.top = e.clientY + 'px';
 					dragImage.style.right = 'auto';
 
-					setDragAction(e, 'messages', e.ctrlKey ? 'copy' : 'move', data, dragImage);
+					setDragAction(e, 'messages', data.copy ? 'copy' : 'move', data, dragImage);
 
 					// Remove the Chrome visibility
 					dragImage.style.cssText = '';
@@ -150,8 +149,8 @@ Object.assign(ko.bindingHandlers, {
 					fnStop(e);
 					if (dragMessages() && ['move','copy'].includes(e.dataTransfer.effectAllowed)) {
 						let data = dragData.data;
-						if (folder && data?.folder && isArray(data.uids)) {
-							moveMessagesToFolder(data.folder, data.uids, folder.fullName, data.copy && e.ctrlKey);
+						if (folder && data?.folder && data.size) {
+							moveMessagesToFolder(data.folder, data, folder.fullName, data.copy && e.ctrlKey);
 						}
 					}
 				}
diff --git a/dev/Stores/User/Messagelist.js b/dev/Stores/User/Messagelist.js
index 0a7d30c41..06ce24cdf 100644
--- a/dev/Stores/User/Messagelist.js
+++ b/dev/Stores/User/Messagelist.js
@@ -107,11 +107,11 @@ addComputablesTo(MessagelistUserStore, {
 	},
 
 	listCheckedOrSelectedUidsWithSubMails: () => {
-		let result = [];
+		let result = new Set;
 		MessagelistUserStore.listCheckedOrSelected().forEach(message => {
-			result.push(message.uid);
+			result.add(message.uid);
 			if (1 < message.threadsLen()) {
-				result = result.concat(message.threads()).unique();
+				message.threads().forEach(result.add, result);
 			}
 		});
 		return result;
@@ -340,15 +340,13 @@ MessagelistUserStore.setAction = (sFolderFullName, iSetAction, messages) => {
 
 /**
  * @param {string} fromFolderFullName
- * @param {Array} uidForRemove
+ * @param {Set} oUids
  * @param {string=} toFolderFullName = ''
  * @param {boolean=} copy = false
  */
 MessagelistUserStore.removeMessagesFromList = (
-	fromFolderFullName, uidForRemove, toFolderFullName = '', copy = false
+	fromFolderFullName, oUids, toFolderFullName = '', copy = false
 ) => {
-	uidForRemove = uidForRemove.map(mValue => pInt(mValue));
-
 	let unseenCount = 0,
 		messageList = MessagelistUserStore,
 		currentMessage = MessageUserStore.message();
@@ -359,7 +357,7 @@ MessagelistUserStore.removeMessagesFromList = (
 		toFolder = toFolderFullName ? getFolderFromCacheList(toFolderFullName) : null,
 		messages =
 			FolderUserStore.currentFolderFullName() === fromFolderFullName
-				? messageList.filter(item => item && uidForRemove.includes(pInt(item.uid)))
+				? messageList.filter(item => item && oUids.has(item.uid))
 				: [];
 
 	messages.forEach(item => item?.isUnseen() && ++unseenCount);
@@ -368,7 +366,7 @@ MessagelistUserStore.removeMessagesFromList = (
 		fromFolder.hash = '';
 		if (!copy) {
 			fromFolder.totalEmails(
-				0 <= fromFolder.totalEmails() - uidForRemove.length ? fromFolder.totalEmails() - uidForRemove.length : 0
+				0 <= fromFolder.totalEmails() - oUids.size ? fromFolder.totalEmails() - oUids.size : 0
 			);
 
 			if (0 < unseenCount) {
@@ -386,7 +384,7 @@ MessagelistUserStore.removeMessagesFromList = (
 			unseenCount = 0;
 		}
 
-		toFolder.totalEmails(toFolder.totalEmails() + uidForRemove.length);
+		toFolder.totalEmails(toFolder.totalEmails() + oUids.size);
 		if (0 < unseenCount) {
 			toFolder.unreadEmails(toFolder.unreadEmails() + unseenCount);
 		}
diff --git a/dev/View/Popup/Compose.js b/dev/View/Popup/Compose.js
index e44dd349a..3e214fd8a 100644
--- a/dev/View/Popup/Compose.js
+++ b/dev/View/Popup/Compose.js
@@ -564,9 +564,9 @@ export class ComposePopupView extends AbstractViewPopup {
 			() => {
 				const
 					sFromFolderFullName = this.draftsFolder(),
-					aUidForRemove = [this.draftUid()];
-				messagesDeleteHelper(sFromFolderFullName, aUidForRemove);
-				MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, aUidForRemove);
+					oUids = new Set([this.draftUid()]);
+				messagesDeleteHelper(sFromFolderFullName, oUids);
+				MessagelistUserStore.removeMessagesFromList(sFromFolderFullName, oUids);
 				this.close();
 			}
 		]);
diff --git a/dev/View/User/MailBox/MessageList.js b/dev/View/User/MailBox/MessageList.js
index 633e3b5e8..8a37fd88b 100644
--- a/dev/View/User/MailBox/MessageList.js
+++ b/dev/View/User/MailBox/MessageList.js
@@ -384,12 +384,9 @@ export class MailMessageList extends AbstractViewRight {
 		const item = ko.dataFor(doc.elementFromPoint(event.clientX, event.clientY));
 		item?.checked?.(true);
 		const uids = MessagelistUserStore.listCheckedOrSelectedUidsWithSubMails();
-		item && !uids.includes(item.uid) && uids.push(item.uid);
-		return uids.length ? {
-			copy: event.ctrlKey,
-			folder: FolderUserStore.currentFolderFullName(),
-			uids: uids
-		} : null;
+		uids.copy = event.ctrlKey; // dropEffect
+		uids.folder = FolderUserStore.currentFolderFullName();
+		return uids;
 	}
 
 	listSetSeen() {
diff --git a/dev/View/User/MailBox/MessageView.js b/dev/View/User/MailBox/MessageView.js
index 69aa95de5..e165ca065 100644
--- a/dev/View/User/MailBox/MessageView.js
+++ b/dev/View/User/MailBox/MessageView.js
@@ -499,7 +499,7 @@ export class MailMessageView extends AbstractViewRight {
 	 * @returns {string}
 	 */
 	printableCheckedMessageCount() {
-		const cnt = MessagelistUserStore.listCheckedOrSelectedUidsWithSubMails().length;
+		const cnt = MessagelistUserStore.listCheckedOrSelectedUidsWithSubMails().size;
 		return 0 < cnt ? (100 > cnt ? cnt : '99+') : '';
 	}