diff --git a/dev/Model/Message.js b/dev/Model/Message.js
index c7808dfa9..7afd6fcbe 100644
--- a/dev/Model/Message.js
+++ b/dev/Model/Message.js
@@ -220,6 +220,10 @@ export class MessageModel extends AbstractModel {
 		return classes.join(' ');
 	}
 
+	indent() {
+		return this.level ? 'margin-left:'+this.level+'em' : null;
+	}
+
 	/**
 	 * @returns {string}
 	 */
diff --git a/dev/Stores/User/Messagelist.js b/dev/Stores/User/Messagelist.js
index 3bf21945d..6bf341a9b 100644
--- a/dev/Stores/User/Messagelist.js
+++ b/dev/Stores/User/Messagelist.js
@@ -264,6 +264,17 @@ MessagelistUserStore.reload = (bDropPagePosition = false, bDropCurrentFolderCach
 
 					disableAutoSelect(true);
 
+					if (collection.ThreadUid) {
+						let refs = {};
+						collection.forEach(msg => {
+							msg.level = 0;
+							if (msg.inReplyTo && refs[msg.inReplyTo]) {
+								msg.level = 1 + refs[msg.inReplyTo].level;
+							}
+							refs[msg.messageId] = msg;
+						});
+					}
+
 					MessagelistUserStore(collection);
 					MessagelistUserStore.isIncomplete(false);
 
diff --git a/dev/Styles/User/MessageList.less b/dev/Styles/User/MessageList.less
index 57b79f9f4..7026f6b5f 100644
--- a/dev/Styles/User/MessageList.less
+++ b/dev/Styles/User/MessageList.less
@@ -38,6 +38,13 @@ html.rl-no-preview-pane {
 		text-transform: capitalize;
 	}
 
+	.reply::before {
+		content: '↳';
+		line-height: 3;
+		position: absolute;
+		margin-left: -1em;
+	}
+
 	.b-footer {
 	    display: flex;
 		flex-shrink: 0;
diff --git a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Requests/THREAD.php b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Requests/THREAD.php
index 9cc5314e5..9175c087b 100644
--- a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Requests/THREAD.php
+++ b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Requests/THREAD.php
@@ -21,7 +21,7 @@ namespace MailSo\Imap\Requests;
 class THREAD extends Request
 {
 	// ORDEREDSUBJECT or REFERENCES or REFS
-	public string $sAlgorithm = '';
+	private string $sAlgorithm = '';
 
 	public string $sCriterias = 'ALL';
 
@@ -41,12 +41,17 @@ class THREAD extends Request
 		parent::__construct($oImapClient);
 	}
 
+	public function setAlgorithm(string $sAlgorithm) : void
+	{
+		$sAlgorithm = \strtoupper($sAlgorithm);
+		if (!$this->oImapClient->hasCapability("THREAD={$sAlgorithm}")) {
+			$this->oImapClient->writeLogException(new \MailSo\RuntimeException("THREAD={$sAlgorithm} is not supported"), \LOG_ERR);
+		}
+		$this->sAlgorithm = $sAlgorithm;
+	}
+
 	public function SendRequestIterateResponse() : iterable
 	{
-		if (!$this->oImapClient->hasCapability(\strtoupper("THREAD={$this->sAlgorithm}"))) {
-			$this->oImapClient->writeLogException(new \MailSo\RuntimeException("THREAD={$this->sAlgorithm} is not supported"), \LOG_ERR);
-		}
-
 		$this->oImapClient->SendRequest(
 			($this->bUid ? 'UID THREAD' : 'THREAD'),
 			array(
diff --git a/snappymail/v/0.0.0/app/libraries/MailSo/Mail/Message.php b/snappymail/v/0.0.0/app/libraries/MailSo/Mail/Message.php
index c5d1233fc..021d4aba4 100644
--- a/snappymail/v/0.0.0/app/libraries/MailSo/Mail/Message.php
+++ b/snappymail/v/0.0.0/app/libraries/MailSo/Mail/Message.php
@@ -497,6 +497,8 @@ class Message implements \JsonSerializable
 
 			'Flags' => $aFlags,
 
+			'InReplyTo' => $this->InReplyTo,
+
 			// https://datatracker.ietf.org/doc/html/rfc8621#section-4.1.1
 			'id' => $this->sEmailId,
 //			'blobId' => $this->sEmailIdBlob,
diff --git a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
index 26e0f06c7..2598bd64e 100644
--- a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
+++ b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
@@ -141,7 +141,6 @@ trait Response
 
 			if (!$sParent) {
 				$mResult['DraftInfo'] = $mResponse->DraftInfo;
-				$mResult['InReplyTo'] = $mResponse->InReplyTo;
 				$mResult['UnsubsribeLinks'] = $mResponse->UnsubsribeLinks;
 				$mResult['References'] = $mResponse->References;
 
diff --git a/snappymail/v/0.0.0/app/templates/Views/User/MailMessageList.html b/snappymail/v/0.0.0/app/templates/Views/User/MailMessageList.html
index 16c721901..636f20b96 100644
--- a/snappymail/v/0.0.0/app/templates/Views/User/MailMessageList.html
+++ b/snappymail/v/0.0.0/app/templates/Views/User/MailMessageList.html
@@ -156,7 +156,7 @@
 			<div class="messageListItem" data-bind="css: lineAsCss()">
 				<div class="messageCheckbox">
 					<div class="checkboxMessage fontastic" data-bind="text: checked() ? '☑' : '☐'"></div>
-				</div><div>
+				</div><div data-bind="attr:{style:indent()}, css:{reply:indent}">
 					<div class="flagParent fontastic"></div>
 					<div class="senderParent actionHandle" data-bind="attr: {'title': senderClearEmailsString}, text: senderEmailsString"></div>
 					<div class="subjectParent actionHandle" data-bind="text: subject"></div>