diff --git a/apps/dav/lib/connector/sabre/principal.php b/apps/dav/lib/connector/sabre/principal.php
index 18f28a916f..787bcdf469 100644
--- a/apps/dav/lib/connector/sabre/principal.php
+++ b/apps/dav/lib/connector/sabre/principal.php
@@ -196,6 +196,14 @@ class Principal implements BackendInterface {
 	 * @return string
 	 */
 	function findByUri($uri, $principalPrefix) {
+		if (substr($uri, 0, 7) === 'mailto:') {
+			$email = substr($uri, 7);
+			$users = $this->userManager->getByEmail($email);
+			if (count($users) === 1) {
+				return $this->principalPrefix . '/' . $users[0]->getUID();
+			}
+		}
+
 		return '';
 	}
 
diff --git a/apps/dav/lib/server.php b/apps/dav/lib/server.php
index 73e24c9a29..edaa7ac855 100644
--- a/apps/dav/lib/server.php
+++ b/apps/dav/lib/server.php
@@ -84,6 +84,9 @@ class Server {
 
 		// acl
 		$acl = new DavAclPlugin();
+		$acl->principalCollectionSet = [
+			'principals/users', 'principals/groups'
+		];
 		$acl->defaultUsernamePath = 'principals/users';
 		$this->server->addPlugin($acl);
 
diff --git a/apps/dav/tests/unit/connector/sabre/principal.php b/apps/dav/tests/unit/connector/sabre/principal.php
index 1747885240..75076e9618 100644
--- a/apps/dav/tests/unit/connector/sabre/principal.php
+++ b/apps/dav/tests/unit/connector/sabre/principal.php
@@ -255,4 +255,19 @@ class Principal extends TestCase {
 	public function testSearchPrincipals() {
 		$this->assertSame([], $this->connector->searchPrincipals('principals/users', []));
 	}
+
+	public function testFindByUri() {
+		$fooUser = $this->getMockBuilder('\OC\User\User')
+			->disableOriginalConstructor()->getMock();
+		$fooUser
+			->expects($this->exactly(1))
+			->method('getUID')
+			->will($this->returnValue('foo'));
+
+		$this->userManager->expects($this->once())->method('getByEmail')->willReturn([
+			$fooUser
+		]);
+		$ret = $this->connector->findByUri('mailto:foo@bar.net', 'principals/users');
+		$this->assertSame('principals/users/foo', $ret);
+	}
 }
diff --git a/lib/private/user/manager.php b/lib/private/user/manager.php
index 4371be134a..37a3e5ba13 100644
--- a/lib/private/user/manager.php
+++ b/lib/private/user/manager.php
@@ -33,6 +33,7 @@
 namespace OC\User;
 
 use OC\Hooks\PublicEmitter;
+use OCP\IUser;
 use OCP\IUserBackend;
 use OCP\IUserManager;
 use OCP\IConfig;
@@ -354,4 +355,17 @@ class Manager extends PublicEmitter implements IUserManager {
 			} while (count($users) >= $limit);
 		}
 	}
+
+	/**
+	 * @param string $email
+	 * @return IUser[]
+	 * @since 9.1.0
+	 */
+	public function getByEmail($email) {
+		$userIds = $this->config->getUsersForUserValue('settings', 'email', $email);
+
+		return array_map(function($uid) {
+			return $this->get($uid);
+		}, $userIds);
+	}
 }
diff --git a/lib/public/iusermanager.php b/lib/public/iusermanager.php
index 6442938a99..00c0bbc872 100644
--- a/lib/public/iusermanager.php
+++ b/lib/public/iusermanager.php
@@ -142,4 +142,11 @@ interface IUserManager {
 	 * @since 9.0.0
 	 */
 	public function callForAllUsers (\Closure $callback, $search = '');
+
+	/**
+	 * @param string $email
+	 * @return IUser[]
+	 * @since 9.1.0
+	 */
+	public function getByEmail($email);
 }