diff --git a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Commands/Messages.php b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Commands/Messages.php
index e35a1f21c..77bb81db9 100644
--- a/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Commands/Messages.php
+++ b/snappymail/v/0.0.0/app/libraries/MailSo/Imap/Commands/Messages.php
@@ -118,7 +118,7 @@ trait Messages
 	 * @throws \MailSo\Net\Exceptions\Exception
 	 * @throws \MailSo\Imap\Exceptions\Exception
 	 */
-	public function MessageAppendStream(string $sFolderName, $rMessageAppendStream, int $iStreamSize, array $aFlagsList = null, int &$iUid = null, int $iDateTime = 0) : ?int
+	public function MessageAppendStream(string $sFolderName, $rMessageAppendStream, int $iStreamSize, array $aFlagsList = null, int $iDateTime = 0) : ?int
 	{
 		$aParams = array(
 			$this->EscapeFolderName($sFolderName),
@@ -138,27 +138,34 @@ trait Messages
 
 		$this->SendRequestGetResponse('APPEND', $aParams);
 
+		return $this->writeMessageStream($rMessageAppendStream);
+	}
+
+	private function writeMessageStream($rMessageStream) : ?int
+	{
 		$this->writeLog('Write to connection stream', LogType::NOTE);
 
-		\MailSo\Base\Utils::MultipleStreamWriter($rMessageAppendStream, array($this->ConnectionResource()));
+		\MailSo\Base\Utils::MultipleStreamWriter($rMessageStream, array($this->ConnectionResource()));
 
 		$this->sendRaw('');
-		$oResponse = $this->getResponse();
-
-		if (null !== $iUid) {
-			$oLast = $oResponse->getLast();
-			if ($oLast
-			 && ResponseType::TAGGED === $oLast->ResponseType
-			 && \is_array($oLast->OptionalResponse)
-			 && !empty($oLast->OptionalResponse[2])
-			 && \is_numeric($oLast->OptionalResponse[2])
-			 && 'APPENDUID' === \strtoupper($oLast->OptionalResponse[0])
+		$oResponses = $this->getResponse();
+		/**
+		 * Can be tagged
+			 S: A003 OK [APPENDUID 1 2001] APPEND completed
+		 * Or untagged
+			 S: * OK [APPENDUID 1 2001] Replacement Message ready
+		 */
+		foreach ($oResponses as $oResponse) {
+			if (\is_array($oResponse->OptionalResponse)
+			 && !empty($oResponse->OptionalResponse[2])
+			 && \is_numeric($oResponse->OptionalResponse[2])
+			 && 'APPENDUID' === \strtoupper($oResponse->OptionalResponse[0])
 			) {
-				$iUid = (int) $oLast->OptionalResponse[2];
+				return (int) $oResponse->OptionalResponse[2];
 			}
 		}
 
-		return $iUid;
+		return null;
 	}
 
 	/**
@@ -206,6 +213,55 @@ trait Messages
 		);
 	}
 
+	/**
+	 * RFC 8508 REPLACE
+	 * Replaces message in specified folder
+	 * When $iUid < 1 it only appends the message
+	 *
+	 * @param resource $rMessageStream
+	 *
+	 * @throws \MailSo\Base\Exceptions\InvalidArgumentException
+	 * @throws \MailSo\Net\Exceptions\Exception
+	 * @throws \MailSo\Imap\Exceptions\Exception
+	 */
+	public function MessageReplaceStream(string $sFolderName, int $iUid, $rMessageStream, int $iStreamSize, array $aFlagsList = null, int $iDateTime = 0) : ?int
+	{
+		if (1 > $iUid || !$this->IsSupported('REPLACE')) {
+			$this->FolderSelect($sFolderName);
+			$iNewUid = $this->MessageAppendStream($sFolderName, $rMessageStream, $iStreamSize, $aFlagsList, $iDateTime);
+			if ($iUid) {
+				$oRange = new SequenceSet([$iUid]);
+				$this->MessageStoreFlag($oRange,
+					array(\MailSo\Imap\Enumerations\MessageFlag::DELETED),
+					\MailSo\Imap\Enumerations\StoreAction::ADD_FLAGS_SILENT
+				);
+				$this->FolderExpunge($oRange);
+			}
+			return $iNewUid;
+		}
+
+		$aParams = array(
+			$iUid,
+			$this->EscapeFolderName($sFolderName),
+			$aFlagsList
+		);
+		if (0 < $iDateTime) {
+			$aParams[] = $this->EscapeString(\gmdate('d-M-Y H:i:s', $iDateTime).' +0000');
+		}
+
+/*
+		// RFC 3516 || RFC 6855 section-4
+		if ($this->IsSupported('BINARY') || $this->IsSupported('UTF8=ACCEPT')) {
+			$aParams[] = '~{'.$iStreamSize.'}';
+		}
+*/
+		$aParams[] = '{'.$iStreamSize.'}';
+
+		$this->SendRequestGetResponse('UID REPLACE', $aParams);
+
+		return $this->writeMessageStream($rMessageStream);
+	}
+
 	/**
 	 * @throws \MailSo\Base\Exceptions\InvalidArgumentException
 	 * @throws \MailSo\Net\Exceptions\Exception
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 4d33b8b31..fc1499462 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
@@ -401,8 +401,8 @@ class MailClient
 			throw new \MailSo\Base\Exceptions\InvalidArgumentException;
 		}
 
-		$this->oImapClient->MessageAppendStream(
-			$sFolderToSave, $rMessageStream, $iMessageStreamSize, $aAppendFlags, $iUid);
+		$iUid = $this->oImapClient->MessageAppendStream(
+			$sFolderToSave, $rMessageStream, $iMessageStreamSize, $aAppendFlags);
 
 		return $this;
 	}
diff --git a/snappymail/v/0.0.0/app/libraries/RainLoop/Providers/AddressBook/KolabAddressBook.php b/snappymail/v/0.0.0/app/libraries/RainLoop/Providers/AddressBook/KolabAddressBook.php
index 1ac1f3489..fdf930841 100644
--- a/snappymail/v/0.0.0/app/libraries/RainLoop/Providers/AddressBook/KolabAddressBook.php
+++ b/snappymail/v/0.0.0/app/libraries/RainLoop/Providers/AddressBook/KolabAddressBook.php
@@ -141,10 +141,14 @@ class KolabAddressBook implements AddressBookInterface
 		$oContact->PopulateDisplayAndFullNameValue();
 
 		$iUID = $oContact->IdContact;
-		$sUUID = $oContact->GetUID();
 
 		$oPrevMessage = $this->MailClient()->Message($this->FolderName(), $iUID);
-		$oVCard = $oPrevMessage ? $this->fetchXCardFromMessage($oPrevMessage) : null;
+		if ($oPrevMessage) {
+			$oVCard = $this->fetchXCardFromMessage($oPrevMessage);
+		} else {
+			$oVCard = null;
+			$iUID = 0;
+		}
 
 		$oMessage = new \MailSo\Mime\Message();
 
@@ -162,7 +166,7 @@ class KolabAddressBook implements AddressBookInterface
 			}
 		}
 
-		$oMessage->SetSubject($sUUID);
+		$oMessage->SetSubject($oContact->GetUID());
 //		$oMessage->SetDate(\time());
 		$oMessage->Headers->AddByName('X-Kolab-Type', 'application/x-vnd.kolab.contact');
 		$oMessage->Headers->AddByName('X-Kolab-Mime-Version', '3.0');
@@ -185,25 +189,13 @@ class KolabAddressBook implements AddressBookInterface
 		$oPart->Body = $oContact->ToXCard($oVCard/*, $oLogger*/);
 		$oMessage->SubParts->append($oPart);
 
-		if ($oPrevMessage) {
-			// Replace Message
-			if (false && $this->ImapClient()->IsSupported('REPLACE')) {
-				// UID REPLACE
-			} else {
-				$this->MailClient()->MessageDelete(
-					$this->FolderName(),
-					new \MailSo\Imap\SequenceSet([$iUID])
-				);
-			}
-		}
-
 		// Store Message
 		$rMessageStream = \MailSo\Base\ResourceRegistry::CreateMemoryResource();
 		$iMessageStreamSize = \MailSo\Base\Utils::MultipleStreamWriter(
 			$oMessage->ToStream(false), array($rMessageStream), 8192, true, true);
 		if (false !== $iMessageStreamSize) {
 			\rewind($rMessageStream);
-			$this->ImapClient()->MessageAppendStream($this->sFolderName, $rMessageStream, $iMessageStreamSize);
+			$this->ImapClient()->MessageReplaceStream($this->sFolderName, $iUID, $rMessageStream, $iMessageStreamSize);
 		}
 
 		return true;
@@ -211,10 +203,14 @@ class KolabAddressBook implements AddressBookInterface
 
 	public function DeleteContacts(string $sEmail, array $aContactIds) : bool
 	{
-		$this->MailClient()->MessageDelete(
-			$this->FolderName(),
-			new \MailSo\Imap\SequenceSet($aContactIds)
-		);
+		try {
+			$this->MailClient()->MessageDelete(
+				$this->FolderName(),
+				new \MailSo\Imap\SequenceSet($aContactIds)
+			);
+			return true;
+		} catch (\Throwable $e) {
+		}
 		return false;
 	}