diff --git a/lib/Db/CollectedAddressMapper.php b/lib/Db/CollectedAddressMapper.php
index 15b4ebe4e5..f7e396c760 100644
--- a/lib/Db/CollectedAddressMapper.php
+++ b/lib/Db/CollectedAddressMapper.php
@@ -22,11 +22,11 @@
 
 namespace OCA\Mail\Db;
 
-use OCP\AppFramework\Db\Mapper;
+use OCP\AppFramework\Db\QBMapper;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\IDBConnection;
 
-class CollectedAddressMapper extends Mapper {
+class CollectedAddressMapper extends QBMapper {
 
 	/**
 	 * @param IDBConnection $db
@@ -40,25 +40,32 @@ public function __construct(IDBConnection $db) {
 	 *
 	 * @param string $userId
 	 * @param string $query
+	 *
 	 * @return CollectedAddress[]
 	 */
 	public function findMatching($userId, $query) {
-		$sql = 'SELECT * FROM *PREFIX*mail_collected_addresses WHERE `user_id` = ? AND (`email` ILIKE ? OR `display_name` ILIKE ?)';
-		$params = [
-			$userId,
-			'%' . $query . '%',
-			'%' . $query . '%',
-		];
-		return $this->findEntities($sql, $params);
+		$qb = $this->db->getQueryBuilder();
+		$dbQuery = $qb
+			->select('*')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)))
+			->andWhere($qb->expr()->orX(
+				$qb->expr()->iLike('email', $qb->createNamedParameter("%$query%")),
+				$qb->expr()->iLike('display_name', $qb->createNamedParameter("%$query%"))
+			));
+
+		return $this->findEntities($dbQuery);
 	}
 
 	public function exists($userId, $email) {
-		$sql = 'SELECT * FROM *PREFIX*mail_collected_addresses WHERE `user_id` = ? AND `email` ILIKE ?';
-		$params = [
-			$userId,
-			$email
-		];
-		return count($this->findEntities($sql, $params)) > 0;
+		$qb = $this->db->getQueryBuilder();
+		$dbQuery = $qb
+			->select('*')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)))
+			->andWhere($qb->expr()->iLike('email', $qb->createNamedParameter($email)));
+
+		return count($this->findEntities($dbQuery)) > 0;
 	}
 
 	public function getTotal() {
@@ -68,7 +75,7 @@ public function getTotal() {
 			->from($this->getTableName());
 		$result = $qb->execute();
 
-		$count = (int) $result->fetchColumn(0);
+		$count = (int)$result->fetchColumn(0);
 		$result->closeCursor();
 		return $count;
 	}
@@ -85,16 +92,10 @@ public function getChunk($minId = null) {
 			->setMaxResults(100);
 		if (!is_null($minId)) {
 			$query = $query->where($qb->expr()->gte('id',
-					$qb->createNamedParameter($minId)));
+				$qb->createNamedParameter($minId)));
 		}
 
-		$result = $query->execute();
-		$rows = $result->fetchAll();
-		$result->closeCursor();
-
-		return array_map(function(array $data) {
-			return CollectedAddress::fromRow($data);
-		}, $rows);
+		return $this->findEntities($query);
 	}
 
 }
diff --git a/lib/Db/LocalAttachmentMapper.php b/lib/Db/LocalAttachmentMapper.php
index c4c932b8f3..2c6a182fb2 100644
--- a/lib/Db/LocalAttachmentMapper.php
+++ b/lib/Db/LocalAttachmentMapper.php
@@ -23,10 +23,10 @@
 namespace OCA\Mail\Db;
 
 use OCP\AppFramework\Db\DoesNotExistException;
-use OCP\AppFramework\Db\Mapper;
+use OCP\AppFramework\Db\QBMapper;
 use OCP\IDBConnection;
 
-class LocalAttachmentMapper extends Mapper {
+class LocalAttachmentMapper extends QBMapper {
 
 	/**
 	 * @param IDBConnection $db
@@ -37,15 +37,21 @@ public function __construct(IDBConnection $db) {
 
 	/**
 	 * @throws DoesNotExistException
+	 *
 	 * @param int $userId
 	 * @param int $id
+	 *
 	 * @return LocalAttachment
 	 */
 	public function find($userId, $id) {
-		$sql = 'SELECT * FROM `' . $this->getTableName() . '` WHERE user_id = ? and id = ?';
-		$params = [$userId, $id];
-
-		return $this->findEntity($sql, $params);
+		$qb = $this->db->getQueryBuilder();
+		$query = $qb
+			->select('*')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)))
+			->andWhere($qb->expr()->eq('id', $qb->createNamedParameter($id)));
+
+		return $this->findEntity($query);
 	}
 
 }
diff --git a/lib/Db/MailAccountMapper.php b/lib/Db/MailAccountMapper.php
index 1efab8b65f..90c5d26dc3 100644
--- a/lib/Db/MailAccountMapper.php
+++ b/lib/Db/MailAccountMapper.php
@@ -24,10 +24,10 @@
 
 namespace OCA\Mail\Db;
 
-use OCP\AppFramework\Db\Mapper;
+use OCP\AppFramework\Db\QBMapper;
 use OCP\IDBConnection;
 
-class MailAccountMapper extends Mapper {
+class MailAccountMapper extends QBMapper {
 
 	/**
 	 * @param IDBConnection $db
@@ -40,31 +40,43 @@ public function __construct(IDBConnection $db) {
 	 *
 	 * @param string $userId
 	 * @param int $accountId
+	 *
 	 * @return MailAccount
 	 */
 	public function find($userId, $accountId) {
-		$sql = 'SELECT * FROM `' . $this->getTableName() . '` WHERE user_id = ? and id = ?';
-		$params = [$userId, $accountId];
+		$qb = $this->db->getQueryBuilder();
+		$query = $qb
+			->select('*')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)))
+			->andWhere($qb->expr()->eq('id', $qb->createNamedParameter($accountId)));
 
-		return $this->findEntity($sql, $params);
+		return $this->findEntity($qb);
 	}
 
 	/**
 	 * Finds all Mail Accounts by user id existing for this user
+	 *
 	 * @param string $userId the id of the user that we want to find
 	 * @param $userId
+	 *
 	 * @return MailAccount[]
 	 */
 	public function findByUserId($userId) {
-		$sql = 'SELECT * FROM ' . $this->getTableName() . ' WHERE user_id = ?';
-		$params = [$userId];
+		$qb = $this->db->getQueryBuilder();
+		$query = $qb
+			->select('*')
+			->from($this->getTableName())
+			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)));
 
-		return $this->findEntities($sql, $params);
+		return $this->findEntities($query);
 	}
 
 	/**
 	 * Saves an User Account into the database
+	 *
 	 * @param MailAccount $account
+	 *
 	 * @return MailAccount
 	 */
 	public function save(MailAccount $account) {