refactor: move add_or_replace_header to email_utils

app/email_utils.py

@@ -1,5 +1,5 @@
 import os
-from email.message import EmailMessage
+from email.message import EmailMessage, Message
 from email.utils import make_msgid, formatdate
 from smtplib import SMTP
 
@@ -197,3 +197,11 @@ def add_dkim_signature(msg: EmailMessage, email_domain: str):
     sig = sig.replace("\n", " ").replace("\r", "")
 
     msg.add_header("DKIM-Signature", sig[len("DKIM-Signature: ") :])
+
+
+def add_or_replace_header(msg: Message, header: str, value: str):
+    try:
+        msg.add_header(header, value)
+    except ValueError:
+        # the header exists already
+        msg.replace_header(header, value)

email_handler.py

@@ -45,7 +45,7 @@ from app.email_utils import (
     send_email,
     add_dkim_signature,
     get_email_domain_part,
-)
+    add_or_replace_header)
 from app.extensions import db
 from app.log import LOG
 from app.models import GenEmail, ForwardEmail, ForwardEmailLog, CustomDomain
@@ -298,14 +298,6 @@ class MailHandler:
         return "250 Message accepted for delivery"
 
 
-def add_or_replace_header(msg: Message, header: str, value: str):
-    try:
-        msg.add_header(header, value)
-    except ValueError:
-        # the header exists already
-        msg.replace_header(header, value)
-
-
 if __name__ == "__main__":
     controller = Controller(MailHandler(), hostname="0.0.0.0", port=20381)