diff --git a/app/config.py b/app/config.py
index ca5e4687..19e03bce 100644
--- a/app/config.py
+++ b/app/config.py
@@ -326,3 +326,9 @@ MAX_SPAM_SCORE = 5.5
 SPAMASSASSIN_HOST = os.environ.get("SPAMASSASSIN_HOST")
 # use a more restrictive score when replying
 MAX_REPLY_PHASE_SPAM_SCORE = 5
+
+PGP_SENDER_PRIVATE_KEY = None
+PGP_SENDER_PRIVATE_KEY_PATH = os.environ.get("PGP_SENDER_PRIVATE_KEY_PATH")
+if PGP_SENDER_PRIVATE_KEY_PATH:
+    with open(get_abs_path(PGP_SENDER_PRIVATE_KEY_PATH)) as f:
+        PGP_SENDER_PRIVATE_KEY = f.read()
diff --git a/example.env b/example.env
index a32277e3..9daba1c7 100644
--- a/example.env
+++ b/example.env
@@ -162,4 +162,7 @@ DISABLE_ONBOARDING=true
 # PLAUSIBLE_DOMAIN=yourdomain.com
 
 # Spamassassin server
-# SPAMASSASSIN_HOST = 127.0.0.1
\ No newline at end of file
+# SPAMASSASSIN_HOST = 127.0.0.1
+
+# if set, used to sign the forwarding emails
+# PGP_SENDER_PRIVATE_KEY_PATH=local_data/private-pgp.asc
\ No newline at end of file