Issue #3396902 by Primsi: SymfonyMailer::mail should handle other exception types

src/Plugin/Mail/SymfonyMailer.php

@@ -374,6 +374,14 @@ class SymfonyMailer implements MailInterface, ContainerFactoryPluginInterface {
         the following headers:<br /><br />@headers',
         ['@exception_message' => $e->getMessage(), '@headers' => $headers]);
     }
+    catch (\Exception $e) {
+      $this->logger->error('An attempt to send an e-mail message failed, and the following error
+        message was returned : @exception_message',
+        [
+          '@exception_message' => $e->getMessage(),
+        ]
+      );
+    }
     return FALSE;
   }