diff --git a/appinfo/routes.php b/appinfo/routes.php
index cd7665b2f0517429302fb300502dbe10dfdd5dfa..5b60986f05fc8d71aba601e32531959f610ab9fa 100644
--- a/appinfo/routes.php
+++ b/appinfo/routes.php
@@ -25,6 +25,8 @@ declare(strict_types=1);
  */
 return [
 	'routes' => [
+		//Maybe invitiation
+		['name' => 'invitation_maybe#tentative', 'url' => '/invitation/tentative/{token}', 'verb' => 'GET'],
 		// User views
 		['name' => 'view#index', 'url' => '/', 'verb' => 'GET'],
 		['name' => 'view#index', 'url' => '/new', 'verb' => 'GET', 'postfix' => 'direct.new'],
diff --git a/lib/Controller/InvitationMaybeController.php b/lib/Controller/InvitationMaybeController.php
new file mode 100755
index 0000000000000000000000000000000000000000..c7fdad4997ff09841b44662f96b8e3afc0e6ce6f
--- /dev/null
+++ b/lib/Controller/InvitationMaybeController.php
@@ -0,0 +1,155 @@
+<?php
+
+declare(strict_types=1);
+namespace OCA\Calendar\Controller;
+
+use OCA\DAV\CalDAV\InvitationResponse\InvitationResponseServer;
+use OCP\AppFramework\Controller;
+use OCP\AppFramework\Http\TemplateResponse;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\IDBConnection;
+use OCP\IRequest;
+use Sabre\VObject\ITip\Message;
+use Sabre\VObject\Reader;
+
+class InvitationMaybeController extends Controller {
+
+	/** @var IDBConnection */
+	private $db;
+
+	/** @var ITimeFactory */
+	private $timeFactory;
+
+	/** @var InvitationResponseServer */
+	private $responseServer;
+
+	/**
+	 * InvitationResponseController constructor.
+	 *
+	 * @param string $appName
+	 * @param IRequest $request
+	 * @param IDBConnection $db
+	 * @param ITimeFactory $timeFactory
+	 * @param InvitationResponseServer $responseServer
+	 */
+	public function __construct(string $appName, IRequest $request,
+								IDBConnection $db, ITimeFactory $timeFactory,
+								InvitationResponseServer $responseServer) {
+		parent::__construct($appName, $request);
+		$this->db = $db;
+		$this->timeFactory = $timeFactory;
+		$this->responseServer = $responseServer;
+		// Don't run `$server->exec()`, because we just need access to the
+		// fully initialized schedule plugin, but we don't want Sabre/DAV
+		// to actually handle and reply to the request
+	}
+	/**
+	 * @PublicPage
+	 * @NoCSRFRequired
+	 *
+	 * @param string $token
+	 * @return TemplateResponse
+	 */
+	public function tentative(string $token):TemplateResponse {
+		$row = $this->getTokenInformation($token);
+		if (!$row) {
+			return new TemplateResponse($this->appName, 'schedule-response-error', [], 'guest');
+		}
+		$iTipMessage = $this->buildITipResponse($row, 'TENTATIVE');
+		$this->responseServer->handleITipMessage($iTipMessage);
+
+		if ($iTipMessage->getScheduleStatus() === '1.2') {
+			return new TemplateResponse($this->appName, 'schedule-response-success', [], 'guest');
+		}
+
+		return new TemplateResponse($this->appName, 'schedule-response-error', [
+			'organizer' => $row['organizer'],
+		], 'guest');
+	}
+
+	/**
+	 * @param array $row
+	 * @param string $partStat participation status of attendee - SEE RFC 5545
+	 * @param int|null $guests
+	 * @param string|null $comment
+	 * @return Message
+	 */
+	private function buildITipResponse(array $row, string $partStat, int $guests = null,
+									   string $comment = null):Message {
+		$iTipMessage = new Message();
+		$iTipMessage->uid = $row['uid'];
+		$iTipMessage->component = 'VEVENT';
+		$iTipMessage->method = 'REPLY';
+		$iTipMessage->sequence = $row['sequence'];
+		$iTipMessage->sender = $row['attendee'];
+
+		if ($this->responseServer->isExternalAttendee($row['attendee'])) {
+			$iTipMessage->recipient = $row['organizer'];
+		} else {
+			$iTipMessage->recipient = $row['attendee'];
+		}
+
+		$message = <<<EOF
+BEGIN:VCALENDAR
+PRODID:-//Nextcloud/Nextcloud CalDAV Server//EN
+METHOD:REPLY
+VERSION:2.0
+BEGIN:VEVENT
+ATTENDEE;PARTSTAT=%s:%s
+ORGANIZER:%s
+UID:%s
+SEQUENCE:%s
+REQUEST-STATUS:2.0;Success
+%sEND:VEVENT
+END:VCALENDAR
+EOF;
+
+		$vObject = Reader::read(vsprintf($message, [
+			$partStat, $row['attendee'], $row['organizer'],
+			$row['uid'], $row['sequence'] ?? 0, $row['recurrenceid'] ?? ''
+		]));
+		$vEvent = $vObject->{'VEVENT'};
+		/** @var \Sabre\VObject\Property\ICalendar\CalAddress $attendee */
+		$attendee = $vEvent->{'ATTENDEE'};
+
+		$vEvent->DTSTAMP = date('Ymd\\THis\\Z', $this->timeFactory->getTime());
+
+		if ($comment) {
+			$attendee->add('X-RESPONSE-COMMENT', $comment);
+			$vEvent->add('COMMENT', $comment);
+		}
+		if ($guests) {
+			$attendee->add('X-NUM-GUESTS', $guests);
+		}
+
+		$iTipMessage->message = $vObject;
+
+		return $iTipMessage;
+	}
+
+
+	/**
+	 * @param string $token
+	 * @return array|null
+	 */
+	private function getTokenInformation(string $token) {
+		$query = $this->db->getQueryBuilder();
+		$query->select('*')
+			->from('calendar_invitations')
+			->where($query->expr()->eq('token', $query->createNamedParameter($token)));
+		$stmt = $query->execute();
+		$row = $stmt->fetch(\PDO::FETCH_ASSOC);
+
+		if (!$row) {
+			return null;
+		}
+
+		$currentTime = $this->timeFactory->getTime();
+		if (((int) $row['expiration']) < $currentTime) {
+			return null;
+		}
+
+		return $row;
+	}
+
+}
\ No newline at end of file
diff --git a/templates/schedule-response-error.php b/templates/schedule-response-error.php
new file mode 100755
index 0000000000000000000000000000000000000000..010ea2ed6cbca605be3de9b0851ea354e2f5d928
--- /dev/null
+++ b/templates/schedule-response-error.php
@@ -0,0 +1,7 @@
+<div class="update">
+	<p class="message"><?php p($l->t('There was an error updating your attendance status.'));?></p>
+	<p class="message"><?php p($l->t('Please contact the organizer directly.'));?></p>
+	<?php if (isset($_['organizer'])): ?>
+		<p class="message"><a href="<?php p($_['organizer']) ?>"><?php p(substr($_['organizer'], 7)) ?></a></p>
+	<?php endif; ?>
+</div>
diff --git a/templates/schedule-response-options.php b/templates/schedule-response-options.php
new file mode 100755
index 0000000000000000000000000000000000000000..f5ebb46cb2614448a94833735f488af22acec852
--- /dev/null
+++ b/templates/schedule-response-options.php
@@ -0,0 +1,34 @@
+<?php
+style('dav', 'schedule-response');
+?>
+
+<div class="update">
+	<form action="" method="post">
+		<fieldset id="partStat">
+			<h2><?php p($l->t('Are you accepting the invitation?')); ?></h2>
+			<div id="selectPartStatForm">
+				<input type="radio" id="partStatAccept" name="partStat" value="ACCEPTED" checked />
+				<label for="partStatAccept">
+					<span><?php p($l->t('Accept')); ?></span>
+				</label>
+
+				<input type="radio" id="partStatTentative" name="partStat" value="TENTATIVE" />
+				<label for="partStatTentative">
+					<span><?php p($l->t('Tentative')); ?></span>
+				</label>
+
+				<input type="radio" class="declined" id="partStatDeclined" name="partStat" value="DECLINED" />
+				<label for="partStatDeclined">
+					<span><?php p($l->t('Decline')); ?></span>
+				</label>
+			</div>
+		</fieldset>
+		<fieldset id="more_options">
+			<input type="number" min="0" name="guests" placeholder="<?php p($l->t('Number of guests')); ?>" />
+			<input type="text" name="comment" placeholder="<?php p($l->t('Comment')); ?>" />
+		</fieldset>
+		<fieldset>
+			<input type="submit" value="<?php p($l->t('Save'));?>">
+		</fieldset>
+	</form>
+</div>
diff --git a/templates/schedule-response-success.php b/templates/schedule-response-success.php
new file mode 100755
index 0000000000000000000000000000000000000000..f60cb1e0fa97ad051c8157df80bc8f4e57cfba79
--- /dev/null
+++ b/templates/schedule-response-success.php
@@ -0,0 +1,4 @@
+<div class="update" style="justify-content: space-around; display: flex;">
+	<span class="icon icon-checkmark-white"></span>
+	<p class="message"><?php p($l->t('Your attendance was updated successfully.'));?></p>
+</div>