Add specific exception in case of GPG encryption failing

src/MDMailerHelper.php

@@ -43,11 +43,16 @@ public static function pgp_encrypt(string $to, string $msg):string {
         }
 
         if ($gpg->addsignkey(MD_CONF_EMAIL::PGP_ENC_KEY) === false) {
-            throw new \Exception("Cannot set private key for GPG encryption");
+            throw new \MDMailerEncryptionFailedException("Cannot set private key for GPG encryption");
         }
 
-        if (empty($msg = $gpg->encrypt($msg))) {
-            throw new \Exception("Failed to sign and encrypt the message");
+        try {
+            if (empty($msg = $gpg->encrypt($msg))) {
+                throw new \MDMailerEncryptionFailedException("Failed to sign and encrypt the message");
+            }
+        }
+        catch (Exception $e) {
+            throw new MDMailerEncryptionFailedException("Failed to sign and encrypt the message to " . $to);
         }
 
         return $msg;