fix header decoding

pyquarantine/__init__.py

@@ -27,7 +27,7 @@ __all__ = [
     "whitelist",
     "QuarantineMilter"]
 
-__version__ = "2.0.5"
+__version__ = "2.0.7"
 
 from pyquarantine import _runtime_patches
 
@@ -100,7 +100,7 @@ class QuarantineMilter(Milter.Base):
             self.logger.warning(f"unable to serialize message as bytes: {e}")
             try:
                 self.logger.warning("try to serialize as str and encode")
-                data = self.msg.as_string().encode(errors="replace")
+                data = self.msg.as_string().encode("ascii", errors="replace")
             except Exception as e:
                 self.logger.error(
                     f"unable to serialize message, giving up: {e}")
@@ -261,7 +261,11 @@ class QuarantineMilter(Milter.Base):
                         v = v.replace("\r", "").replace("\n", "")
                         value = Header(s=v).encode()
 
-            self.fp.write(field.encode() + b": " + value.encode() + b"\r\n")
+            # remove surrogates
+            field = field.encode("ascii", errors="replace")
+            value = value.encode("ascii", errors="replace")
+
+            self.fp.write(field + b": " + value + b"\r\n")
         except Exception as e:
             self.logger.exception(
                 f"an exception occured in header method: {e}")