use 7bit as default encoding

app/email_utils.py

@@ -677,27 +677,30 @@ def get_encoding(msg: Message) -> str:
     """
     Return the message encoding, possible values:
     - quoted-printable
-    - base64: default if unknown
+    - base64
+    - 7bit: default if unknown or empty
     """
     cte = str(msg.get("content-transfer-encoding", "")).lower()
-    if cte == "":
+    if cte in ("", "7bit"):
-        return "base64"
+        return "7bit"
 
-    if cte == "quoted-printable" or cte == "base64":
+    if cte in ("quoted-printable", "base64"):
         return cte
 
     LOG.exception("Unknown encoding %s", cte)
 
-    return "base64"
+    return "7bit"
 
 
-def encode_text(text: str, encoding: str = "base64") -> str:
+def encode_text(text: str, encoding: str = "7bit") -> str:
     if encoding == "quoted-printable":
         encoded = quopri.encodestring(text.encode("utf-8"))
         return str(encoded, "utf-8")
-    else:  # use base64 by default
+    elif encoding == "base64":
         encoded = base64.b64encode(text.encode("utf-8"))
         return str(encoded, "utf-8")
+    else:  # 7bit - no encoding
+        return text
 
 
 def add_header(msg: Message, text_header, html_header) -> Message:

tests/test_email_utils.py

@@ -422,19 +422,24 @@ def test_normalize_reply_email(flask_client):
 
 def test_get_encoding():
     msg = email.message_from_string("")
-    assert get_encoding(msg) == "base64"
+    assert get_encoding(msg) == "7bit"
 
     msg = email.message_from_string("Content-TRANSFER-encoding: Invalid")
-    assert get_encoding(msg) == "base64"
+    assert get_encoding(msg) == "7bit"
 
     msg = email.message_from_string("Content-TRANSFER-encoding: quoted-printable")
     assert get_encoding(msg) == "quoted-printable"
 
+    msg = email.message_from_string("Content-TRANSFER-encoding: base64")
+    assert get_encoding(msg) == "base64"
+
 
 def test_encode_text():
     assert encode_text("") == ""
-    assert encode_text("ascii") == "YXNjaWk="
+    assert encode_text("ascii") == "ascii"
+    assert encode_text("ascii", "base64") == "YXNjaWk="
     assert encode_text("ascii", "quoted-printable") == "ascii"
 
-    assert encode_text("mèo méo") == "bcOobyBtw6lv"
+    assert encode_text("mèo méo") == "mèo méo"
+    assert encode_text("mèo méo", "base64") == "bcOobyBtw6lv"
     assert encode_text("mèo méo", "quoted-printable") == "m=C3=A8o m=C3=A9o"