diff --git a/lib/private/User/AccountMapper.php b/lib/private/User/AccountMapper.php
index 0817f9542dc0..3d64f616154b 100644
--- a/lib/private/User/AccountMapper.php
+++ b/lib/private/User/AccountMapper.php
@@ -108,9 +108,11 @@ public function getByEmail($email) {
 			throw new \InvalidArgumentException('$email must be defined');
 		}
 		$qb = $this->db->getQueryBuilder();
+		// RFC 5321 says that only domain name is case insensitive, but in practice
+		// it's the whole email
 		$qb->select('*')
 			->from($this->getTableName())
-			->where($qb->expr()->eq('email', $qb->createNamedParameter($email)));
+			->where($qb->expr()->eq($qb->createFunction('LOWER(`email`)'), $qb->createFunction('LOWER(' . $qb->createNamedParameter($email) . ')')));
 
 		return $this->findEntities($qb->getSQL(), $qb->getParameters());
 	}
diff --git a/tests/lib/User/AccountMapperTest.php b/tests/lib/User/AccountMapperTest.php
index 85b6607c8ac1..dc66acc14e45 100644
--- a/tests/lib/User/AccountMapperTest.php
+++ b/tests/lib/User/AccountMapperTest.php
@@ -120,11 +120,32 @@ public function testFindByDisplayName() {
 		$this->assertEquals("TestFind2", array_shift($result)->getUserId());
 	}
 
+	public function findByEmailDataProvider() {
+		return [
+			['test3@find.tld'],
+			['Test3@find.tld'],
+			['test3@Find.tld'],
+		];
+	}
+
 	/**
 	 * find by email
+	 *
+	 * @dataProvider findByEmailDataProvider
+	 */
+	public function testFindByEmail($email) {
+		$result = $this->mapper->find($email);
+		$this->assertEquals(1, count($result));
+		$this->assertEquals("TestFind3", array_shift($result)->getUserId());
+	}
+
+	/**
+	 * get by email
+	 *
+	 * @dataProvider findByEmailDataProvider
 	 */
-	public function testFindByEmail() {
-		$result= $this->mapper->find('test3@find.tld');
+	public function testGetByEmail($email) {
+		$result = $this->mapper->getByEmail($email);
 		$this->assertEquals(1, count($result));
 		$this->assertEquals("TestFind3", array_shift($result)->getUserId());
 	}
@@ -148,4 +169,4 @@ public function testFindLimitAndOffset() {
 		$this->assertEquals("TestFind3", array_shift($result)->getUserId());
 		$this->assertEquals("TestFind4", array_shift($result)->getUserId());
 	}
-}
\ No newline at end of file
+}