diff --git a/dev/Stores/User/Messagelist.js b/dev/Stores/User/Messagelist.js
index 4be5c9d9fd..9463e762de 100644
--- a/dev/Stores/User/Messagelist.js
+++ b/dev/Stores/User/Messagelist.js
@@ -134,7 +134,7 @@ MessagelistUserStore.initUidNextAndNewMessages = (folder, uidNext, newMessages)
 				newMessages.forEach(item => {
 					NotificationUserStore.displayDesktopNotification(
 						EmailCollectionModel.reviveFromJson(item.From).toString(),
-						item.Subject,
+						item.subject,
 						{ Folder: item.Folder, Uid: item.Uid }
 					);
 				});
diff --git a/dev/View/Popup/Compose.js b/dev/View/Popup/Compose.js
index cc366ab4d8..cbab218154 100644
--- a/dev/View/Popup/Compose.js
+++ b/dev/View/Popup/Compose.js
@@ -455,7 +455,7 @@ export class ComposePopupView extends AbstractViewPopup {
 				Cc: this.cc(),
 				Bcc: this.bcc(),
 				ReplyTo: this.replyTo(),
-				Subject: this.subject(),
+				subject: this.subject(),
 				DraftInfo: this.aDraftInfo,
 				InReplyTo: this.sInReplyTo,
 				References: this.sReferences,
diff --git a/dev/View/User/MailBox/MessageView.js b/dev/View/User/MailBox/MessageView.js
index 75768be083..a31e6e03a9 100644
--- a/dev/View/User/MailBox/MessageView.js
+++ b/dev/View/User/MailBox/MessageView.js
@@ -575,7 +575,7 @@ export class MailMessageView extends AbstractViewRight {
 				MessageFolder: oMessage.folder,
 				MessageUid: oMessage.uid,
 				ReadReceipt: oMessage.readReceipt(),
-				Subject: i18n('READ_RECEIPT/SUBJECT', { SUBJECT: oMessage.subject() }),
+				subject: i18n('READ_RECEIPT/SUBJECT', { SUBJECT: oMessage.subject() }),
 				Text: i18n('READ_RECEIPT/BODY', { 'READ-RECEIPT': AccountUserStore.email() })
 			});
 		}
diff --git a/snappymail/v/0.0.0/app/libraries/MailSo/Mail/MailClient.php b/snappymail/v/0.0.0/app/libraries/MailSo/Mail/MailClient.php
index 1dbd2b591b..367f7190a1 100644
--- a/snappymail/v/0.0.0/app/libraries/MailSo/Mail/MailClient.php
+++ b/snappymail/v/0.0.0/app/libraries/MailSo/Mail/MailClient.php
@@ -504,7 +504,7 @@ private function getFolderNextMessageInformation(string $sFolderName, int $iPrev
 					$aNewMessages[] = array(
 						'Folder' => $sFolderName,
 						'Uid' => $iUid,
-						'Subject' => $oHeaders->ValueByName(MimeHeader::SUBJECT, !$sContentTypeCharset),
+						'subject' => $oHeaders->ValueByName(MimeHeader::SUBJECT, !$sContentTypeCharset),
 						'From' => $oHeaders->GetAsEmailCollection(MimeHeader::FROM_, !$sContentTypeCharset)
 					);
 				}
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 90e1180534..c1f0e9e5ef 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
@@ -632,9 +632,8 @@ public function jsonSerialize()
 			'@Object' => 'Object/Message',
 			'Folder' => $this->sFolder,
 			'Uid' => $this->iUid,
-			'Subject' => \trim(Utils::Utf8Clear($this->sSubject)),
+			'subject' => \trim(Utils::Utf8Clear($this->sSubject)),
 			'MessageId' => $this->sMessageId,
-			'Size' => $this->iSize,
 			'SpamScore' => $this->bIsSpam ? 100 : $this->iSpamScore,
 			'SpamResult' => $this->sSpamResult,
 			'IsSpam' => $this->bIsSpam,
@@ -658,7 +657,12 @@ public function jsonSerialize()
 
 			'Attachments' => $this->oAttachments ? $this->oAttachments->SpecData() : null,
 
-			'Flags' => $this->aFlagsLowerCase
+			'Flags' => $this->aFlagsLowerCase,
+
+			// https://datatracker.ietf.org/doc/html/rfc8621#section-4.1.1
+			'size' => $this->iSize,
+			'receivedAt' => \gmdate('Y-m-d\\TH:i:s\\Z', $this->iInternalTimeStampInUTC)
+//			'keywords' => \array_fill_keys($this->aFlagsLowerCase, true)
 		);
 	}
 }
diff --git a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Messages.php b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Messages.php
index 97f69a2648..e2829feafe 100644
--- a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Messages.php
+++ b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Messages.php
@@ -982,7 +982,7 @@ private function cacherForThreads()
 	private function buildReadReceiptMessage(Account $oAccount) : \MailSo\Mime\Message
 	{
 		$sReadReceipt = $this->GetActionParam('ReadReceipt', '');
-		$sSubject = $this->GetActionParam('Subject', '');
+		$sSubject = $this->GetActionParam('subject', '');
 		$sText = $this->GetActionParam('Text', '');
 
 		$oIdentity = $this->GetIdentityByID($oAccount, '', true);
@@ -1084,7 +1084,7 @@ private function buildMessage(Account $oAccount, bool $bWithDraftInfo = true) :
 			$oMessage->SetPriority(\MailSo\Mime\Enumerations\MessagePriority::HIGH);
 		}
 
-		$oMessage->SetSubject($this->GetActionParam('Subject', ''));
+		$oMessage->SetSubject($this->GetActionParam('subject', ''));
 
 		$oToEmails = new \MailSo\Mime\EmailCollection($this->GetActionParam('To', ''));
 		if ($oToEmails->count()) {
diff --git a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
index 14774e5dfb..c5bbaf65a6 100644
--- a/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
+++ b/snappymail/v/0.0.0/app/libraries/RainLoop/Actions/Response.php
@@ -183,7 +183,7 @@ private function responseObject($mResponse, string $sParent = '')
 				$mResult[$prop] = $this->responseObject($mResult[$prop], $sParent);
 			}
 
-			$sSubject = $mResult['Subject'];
+			$sSubject = $mResult['subject'];
 			$mResult['Hash'] = \md5($mResult['Folder'].$mResult['Uid']);
 			$mResult['RequestHash'] = Utils::EncodeKeyValuesQ(array(
 				'V' => APP_VERSION,