diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9e0aedb824..955896a797 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -79,4 +79,4 @@ jobs:
         run: |
           rm -r public_html # remove once https://github.com/phpstan/phpstan/issues/10321 is fixed
           mkdir node_modules # remove once https://github.com/phpstan/phpstan/issues/11436 is fixed
-          vendor/bin/phpstan analyse
+          vendor/bin/phpstan analyse -v
diff --git a/composer.json b/composer.json
index 94a70f134a..fdd7dc213a 100644
--- a/composer.json
+++ b/composer.json
@@ -24,6 +24,7 @@
         "phpstan/extension-installer": "^1.1",
         "phpstan/phpstan": "^1.2",
         "phpstan/phpstan-deprecation-rules": "^1.2",
+        "phpstan/phpstan-strict-rules": "^1.3",
         "phpunit/phpunit": "^9.6.20 || ^10.0 || ^11.0",
         "roundcube/acl": "*",
         "roundcube/additional_message_headers": "*",
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index fee816962a..0e6ee8f236 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -11,6 +11,26 @@ parameters:
         - vendor
 
     ignoreErrors:
+        # relax strict rules
+        - '~^Only booleans are allowed in .+, .+ given( on the (left|right) side)?\.~'
+        - '~^Variable (static )?(property access|method call) on .+\.~'
+        - '~^Variable variables are not allowed.~'
+        - '~^Variable .* might not be defined\.~'
+        - '~Call to function array_filter\(\) requires parameter #2 to be passed to avoid loose comparison semantics.~'
+        # TODO
+        - '~^Dynamic call to static method .+\.~' # TODO in https://github.com/roundcube/roundcubemail/pull/9314
+        - '~^Construct empty\(\) is not allowed\. Use more strict comparison\.~'
+        - '~^Loose comparison via "[=!]=" is not allowed\.~'
+        - '~^Casting to .+ something that''s already .+\.~'
+        - '~^Short ternary operator is not allowed\. Use null coalesce operator if applicable or consider using long ternary\.~'
+        - '~^Call to function (array_search|in_array)\(\) requires parameter #3 to be set\.~'
+        - '~^Call to function base64_decode\(\) requires parameter #2 to be (set|true).~'
+
+        -
+            message: '~^Parameter #1 \$browser \(Roundcube\\Tests\\Browser\\Browser\) of method Roundcube\\Tests\\Browser\\Components\\\w+::assert\(\) should be contravariant with parameter \$browser \(Laravel\\Dusk\\Browser\) of method Laravel\\Dusk\\Component::assert\(\)$~'
+            count: 7
+            path: tests/Browser/Components/*.php
+
         # https://github.com/php/pecl-authentication-krb5
         -
             path: 'program/lib/Roundcube/rcube_imap_generic.php'
diff --git a/plugins/managesieve/managesieve.php b/plugins/managesieve/managesieve.php
index 1e160b60f8..910e285cb6 100644
--- a/plugins/managesieve/managesieve.php
+++ b/plugins/managesieve/managesieve.php
@@ -60,8 +60,8 @@ public function init()
         $this->register_action('plugin.managesieve-save', [$this, 'managesieve_save']);
         $this->register_action('plugin.managesieve-saveraw', [$this, 'managesieve_saveraw']);
 
-        $task = $this->rc->task ?? null;
-        $action = $this->rc->action ?? null;
+        $task = $this->rc->task ?? null; // @phpstan-ignore-line
+        $action = $this->rc->action ?? null; // @phpstan-ignore-line
 
         if ($task == 'settings') {
             $this->add_hook('settings_actions', [$this, 'settings_actions']);
diff --git a/program/actions/contacts/delete.php b/program/actions/contacts/delete.php
index 3933e17555..5657bfad82 100644
--- a/program/actions/contacts/delete.php
+++ b/program/actions/contacts/delete.php
@@ -41,6 +41,7 @@ public function run($args = [])
         foreach ($cids as $source => $cid) {
             $CONTACTS = self::contact_source($source);
 
+            // @phpstan-ignore-next-line
             if ($CONTACTS->readonly && empty($CONTACTS->deletable)) {
                 // more sources? do nothing, probably we have search results from
                 // more than one source, some of these sources can be readonly
diff --git a/program/actions/contacts/move.php b/program/actions/contacts/move.php
index 0649d94b40..399520456c 100644
--- a/program/actions/contacts/move.php
+++ b/program/actions/contacts/move.php
@@ -63,6 +63,7 @@ public function run($args = [])
                 break;
             }
 
+            // @phpstan-ignore-next-line
             if (!$CONTACTS || !$CONTACTS->ready || ($CONTACTS->readonly && empty($CONTACTS->deletable))) {
                 continue;
             }
diff --git a/program/actions/contacts/save.php b/program/actions/contacts/save.php
index cf4bd23778..0cf5100e1a 100644
--- a/program/actions/contacts/save.php
+++ b/program/actions/contacts/save.php
@@ -245,6 +245,7 @@ public static function process_input()
 
                 foreach ($subtypes as $i => $subtype) {
                     $suffix = $subtype ? ":{$subtype}" : '';
+                    // @phpstan-ignore-next-line
                     if (!empty($values[$i])) {
                         $record[$col . $suffix][] = $values[$i];
                     }
diff --git a/program/actions/mail/compose.php b/program/actions/mail/compose.php
index 900fc8161d..9961d895cd 100644
--- a/program/actions/mail/compose.php
+++ b/program/actions/mail/compose.php
@@ -1639,7 +1639,7 @@ public static function save_attachment($message, $pid, $compose_id, $params = []
             $filename = !empty($params['filename']) ? $params['filename'] : self::attachment_name($part);
         } elseif ($message instanceof rcube_message) {
             // the whole message requested
-            $size = $message->size ?? null;
+            $size = $message->size ?? null; // @phpstan-ignore-line
             $mimetype = 'message/rfc822';
             $filename = !empty($params['filename']) ? $params['filename'] : 'message_rfc822.eml';
         } elseif (is_string($message)) {
diff --git a/program/include/rcmail.php b/program/include/rcmail.php
index 53884058cc..dbaafa7c22 100644
--- a/program/include/rcmail.php
+++ b/program/include/rcmail.php
@@ -56,7 +56,7 @@ class rcmail extends rcube
     public $oauth;
 
     /** @var rcmail_output_cli|rcmail_output_html|rcmail_output_json|null Output handler */
-    public $output;
+    public $output; // @phpstan-ignore-line
 
     private $address_books = [];
     private $action_args = [];
diff --git a/program/include/rcmail_sendmail.php b/program/include/rcmail_sendmail.php
index aa0f0f8653..bdd522e920 100644
--- a/program/include/rcmail_sendmail.php
+++ b/program/include/rcmail_sendmail.php
@@ -457,6 +457,7 @@ public function deliver_message($message, $disconnect = true)
             return false;
         }
 
+        // @phpstan-ignore-next-line
         if ($mailbody_file) {
             $this->temp_files[$message->headers()['Message-ID']] = $mailbody_file;
         }
diff --git a/program/lib/Roundcube/rcube.php b/program/lib/Roundcube/rcube.php
index c0b409a136..ebcbeef755 100644
--- a/program/lib/Roundcube/rcube.php
+++ b/program/lib/Roundcube/rcube.php
@@ -659,9 +659,9 @@ public function text_exists($name, $domain = null, &$ref_domain = null)
 
         // any of loaded domains (plugins)
         if ($domain == '*') {
-            foreach ($this->plugins->loaded_plugins() as $domain) {
-                if (isset($this->texts[$domain . '.' . $name])) {
-                    $ref_domain = $domain;
+            foreach ($this->plugins->loaded_plugins() as $domain2) {
+                if (isset($this->texts[$domain2 . '.' . $name])) {
+                    $ref_domain = $domain2;
                     return true;
                 }
             }
diff --git a/program/lib/Roundcube/rcube_imap.php b/program/lib/Roundcube/rcube_imap.php
index cc41965a39..7d27c3b5c3 100644
--- a/program/lib/Roundcube/rcube_imap.php
+++ b/program/lib/Roundcube/rcube_imap.php
@@ -4368,7 +4368,6 @@ public function sort_folder_list($a_folders, $skip_special = false)
         }
 
         // Force the type of folder name variable (#1485527)
-        /** @var array<string|null> $folders */
         $folders = array_map('strval', $folders);
 
         $count = count($folders);
diff --git a/program/lib/Roundcube/rcube_washtml.php b/program/lib/Roundcube/rcube_washtml.php
index 5560e890ef..53362bf116 100644
--- a/program/lib/Roundcube/rcube_washtml.php
+++ b/program/lib/Roundcube/rcube_washtml.php
@@ -593,7 +593,7 @@ private function dumpHtml($node, $level = 20)
                             }
 
                             foreach ($ns_nodes as $ns) {
-                                if (isset($ns->nodeName) && isset($ns->nodeValue)
+                                if (isset($ns->nodeName) && isset($ns->nodeValue) // @phpstan-ignore property.notFound
                                     && $ns->nodeName != 'xmlns:xml'
                                     && preg_match('/^[a-zA-Z:-]+$/', $ns->nodeName)
                                     && strpos($ns->nodeValue, '://')
diff --git a/tests/Actions/Contacts/QrcodeTest.php b/tests/Actions/Contacts/QrcodeTest.php
index 5a52c2a6cb..8e6aefb26b 100644
--- a/tests/Actions/Contacts/QrcodeTest.php
+++ b/tests/Actions/Contacts/QrcodeTest.php
@@ -25,7 +25,7 @@ public function test_run()
 
         $result = $output->getOutput();
 
-        $this->assertCOntains('HTTP/1.0 404 Contact not found', $output->headers);
+        $this->assertContains('HTTP/1.0 404 Contact not found', $output->headers);
         $this->assertSame('', $result);
 
         $type = $action->check_support();
diff --git a/tests/Framework/MessageTest.php b/tests/Framework/MessageTest.php
index 876771b532..0b29a8d023 100644
--- a/tests/Framework/MessageTest.php
+++ b/tests/Framework/MessageTest.php
@@ -94,7 +94,7 @@ class rcube_message_test extends \rcube_message
 {
     private $part_bodies = [];
 
-    public function __construct($uid, $folder = null, $is_safe = false)
+    public function __construct($uid, $folder = null, $is_safe = false) // @phpstan-ignore constructor.missingParentCall
     {
         $this->uid = $uid;
         $this->folder = $folder;