diff --git a/lib/BackgroundJob/IMipMessageJob.php b/lib/BackgroundJob/IMipMessageJob.php
index bb0fa95fda..48a5f5904e 100644
--- a/lib/BackgroundJob/IMipMessageJob.php
+++ b/lib/BackgroundJob/IMipMessageJob.php
@@ -32,16 +32,14 @@
 use function method_exists;
 
 class IMipMessageJob extends TimedJob {
-
-	/** @var IMipService */
-	private $iMipService;
+	private IMipService $iMipService;
 
 	public function __construct(ITimeFactory $time,
 								IMipService $iMipService) {
 		parent::__construct($time);
 
 		// Run once per hour
-		$this->setInterval(60*60);
+		$this->setInterval(60 * 60);
 		/**
 		 * @todo remove checks with 24+
 		 */
diff --git a/lib/Db/MessageMapper.php b/lib/Db/MessageMapper.php
index 6ad21e2f13..c81407fe7b 100644
--- a/lib/Db/MessageMapper.php
+++ b/lib/Db/MessageMapper.php
@@ -1239,7 +1239,7 @@ public function findIMipMessages(): array {
 				$qb->expr()->eq('imip_message', $qb->createNamedParameter(true, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
 				$qb->expr()->eq('imip_processed', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
 				$qb->expr()->eq('imip_error', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
-				$qb->expr()->gt('sent_at', ($this->timeFactory->getTime() - 60*60*24*14), $qb->createNamedParameter(false, IQueryBuilder::PARAM_INT)),
+				$qb->expr()->gt('sent_at', ($this->timeFactory->getTime() - 60 * 60 * 24 * 14), $qb->createNamedParameter(false, IQueryBuilder::PARAM_INT)),
 			);
 
 		return $this->findEntities($select);
diff --git a/lib/Migration/Version1140Date20220630113356.php b/lib/Migration/Version1140Date20220630113356.php
index c4a80d7568..2384c75162 100644
--- a/lib/Migration/Version1140Date20220630113356.php
+++ b/lib/Migration/Version1140Date20220630113356.php
@@ -44,19 +44,19 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 		$schema = $schemaClosure();
 
 		$messagesTable = $schema->getTable('mail_messages');
-		if(!$messagesTable->hasColumn('imip_message')) {
+		if (!$messagesTable->hasColumn('imip_message')) {
 			$messagesTable->addColumn('imip_message', 'boolean', [
 				'notnull' => false,
 				'default' => false,
 			]);
 		}
-		if(!$messagesTable->hasColumn('imip_processed')) {
+		if (!$messagesTable->hasColumn('imip_processed')) {
 			$messagesTable->addColumn('imip_processed', 'boolean', [
 				'notnull' => false,
 				'default' => false,
 			]);
 		}
-		if(!$messagesTable->hasColumn('imip_error')) {
+		if (!$messagesTable->hasColumn('imip_error')) {
 			$messagesTable->addColumn('imip_error', 'boolean', [
 				'notnull' => false,
 				'default' => false,
diff --git a/lib/Service/IMipService.php b/lib/Service/IMipService.php
index 527a362d83..6974de450d 100644
--- a/lib/Service/IMipService.php
+++ b/lib/Service/IMipService.php
@@ -26,20 +26,23 @@
 
 namespace OCA\Mail\Service;
 
-use OCA\Mail\Db\MailAccountMapper;
+use OCA\Mail\Account;
 use OCA\Mail\Db\Mailbox;
 use OCA\Mail\Db\MailboxMapper;
 use OCA\Mail\Db\Message;
 use OCA\Mail\Db\MessageMapper;
+use OCA\Mail\Exception\ServiceException;
 use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\Calendar\IManager;
+use Psr\Log\LoggerInterface;
 
 class IMipService {
-
 	private MessageMapper $messageMapper;
 	private MailboxMapper $mailboxMapper;
 	private AccountService $accountService;
 	private MailManager $mailManager;
+	private IManager $calendarManager;
+	private LoggerInterface $logger;
 
 	public function __construct(
 		MessageMapper $messageMapper,
@@ -47,31 +50,33 @@ public function __construct(
 		AccountService $accountService,
 		MailManager $mailManager,
 		IManager $manager,
+		LoggerInterface $logger,
 	) {
 		$this->messageMapper = $messageMapper;
 		$this->mailboxMapper = $mailboxMapper;
 		$this->accountService = $accountService;
 		$this->mailManager = $mailManager;
+		$this->calendarManager = $manager;
+		$this->logger = $logger;
 	}
 
 	public function process() {
 		$messages = $this->messageMapper->findIMipMessages();
 
+		// Collect all mailboxes in memory
 		$mailboxIds = array_unique(array_map(function (Message $message) {
 			return $message->getMailboxId();
 		}, $messages));
 
 		$mailboxes = array_combine($mailboxIds, array_map(function (int $mailboxId) {
 			try {
-				$mailbox = $this->mailboxMapper->findById($mailboxId);
-				if ($mailbox->getSpecialUse() === '["sent"]' || $mailbox->getSpecialUse() === '["drafts"]') {
-					return null;
-				}
+				return $this->mailboxMapper->findById($mailboxId);
 			} catch (DoesNotExistException $e) {
 				return null;
 			}
 		}, $mailboxIds));
 
+		// Collect all accounts in memory
 		$accountIds = array_unique(array_map(function (Mailbox $mailbox) {
 			return $mailbox->getAccountId();
 		}, $mailboxes));
@@ -84,25 +89,57 @@ public function process() {
 			}
 		}, $accountIds));
 
+		// build the updated messages on a per-account basis, so we can bulk update for each account
+		$processedMessages = [];
+		foreach ($messages as $message) {
+			/** @var Mailbox $mailbox */
+			$mailbox = $mailboxes[$message->getMailboxId()];
+			/** @var Account $account */
+			$account = $accounts[$mailbox->getAccountId()];
+			// mailbox not in collated array, maybe specal use?
+			// no processing for drafts and sent items
+			if ($mailbox->getSpecialUse() === '["sent"]' || $mailbox->getSpecialUse() === '["drafts"]') { // does this need more use cases? Also probably won't work? @todo
+				$message->setImipProcessed(true); // Silently drop from passing to DAV and mark as processed, so we won't run into this message again.
+				$processedMessages[$account->getId()] = $message;
+				continue;
+			}
 
 
-		foreach ($messages as $message) {
-			$imapMessage = $this->mailManager->getImapMessage($accounts[$message->getAccountId()], $mailboxes[$message->getMailboxId()], $message->getUid());
+			try {
+				$imapMessage = $this->mailManager->getImapMessage($account, $mailbox, $message->getUid());
+			} catch (ServiceException $e) {
+				$message->setImipError(true);
+				$processedMessages[$account->getId()] = $message;
+				continue;
+			}
 
-			if(empty($imapMessage->scheduling)) {
+			if (empty($imapMessage->scheduling)) {
 				// No scheduling info, maybe the DB is wrong
 				$message->setImipError(true);
-				$this->messageMapper->update($message);
+				$processedMessages[$account->getId()] = $message;
 				continue;
 			}
 
-			if($imapMessage->scheduling['method'] === 'REPLY' || $imapMessage->scheduling['method'] == 'CANCEL') {
-				// automatically process this
-
-				$message->setImipProcessed(true);
-				$this->messageMapper->update($message);
+			$principalUri = '';
+			$sender = $imapMessage->getFrom()->first()->getEmail();
+			$recipient = $account->getEmail();
+			$processed = false;
+			if ($imapMessage->scheduling['method'] === 'REPLY') {
+				$processed = $this->calendarManager->handleIMipReply($principalUri, $sender, $recipient, $imapMessage->scheduling['content']);
+			} elseif ($imapMessage->scheduling['method'] === 'CANCEL') {
+				$processed = $this->calendarManager->handleIMipCancel($principalUri, $sender, $recipient, $imapMessage->scheduling['content']);
 			}
+			$message->setImipProcessed($processed);
+			$message->setImipError(!$processed);
+			$processedMessages[$account->getId()] = $message;
 		}
 
+		foreach ($processedMessages as $accountId => $messages) {
+			try {
+				$this->messageMapper->updateBulk($accounts[$accountId], false, $messages);
+			} catch (\Throwable $e) {
+				$this->logger->error('Could not update iMip messages for account ' . $accountId, ['exception' => $e]);
+			}
+		}
 	}
 }