diff --git a/changelog.d/11710.bugfix b/changelog.d/11710.bugfix
new file mode 100644
index 000000000000..6521a37f6eb9
--- /dev/null
+++ b/changelog.d/11710.bugfix
@@ -0,0 +1 @@
+Fix a bug introduced in Synapse v1.18.0 where password reset and address validation emails would not be sent if their subject was configured to use the 'app' template variable. Contributed by @br4nnigan.
diff --git a/changelog.d/11745.bugfix b/changelog.d/11745.bugfix
new file mode 100644
index 000000000000..6521a37f6eb9
--- /dev/null
+++ b/changelog.d/11745.bugfix
@@ -0,0 +1 @@
+Fix a bug introduced in Synapse v1.18.0 where password reset and address validation emails would not be sent if their subject was configured to use the 'app' template variable. Contributed by @br4nnigan.
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index ff904c2b4a2f..dadfc574134c 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -178,7 +178,7 @@ async def send_registration_mail(
         await self.send_email(
             email_address,
             self.email_subjects.email_validation
-            % {"server_name": self.hs.config.server.server_name},
+            % {"server_name": self.hs.config.server.server_name, "app": self.app_name},
             template_vars,
         )
 
@@ -209,7 +209,7 @@ async def send_add_threepid_mail(
         await self.send_email(
             email_address,
             self.email_subjects.email_validation
-            % {"server_name": self.hs.config.server.server_name},
+            % {"server_name": self.hs.config.server.server_name, "app": self.app_name},
             template_vars,
         )