diff --git a/email_handler.py b/email_handler.py
index 00608592..bd70b37d 100644
--- a/email_handler.py
+++ b/email_handler.py
@@ -31,7 +31,7 @@ It should contain the following info:
 
 """
 import time
-from email.message import EmailMessage
+from email.message import Message
 from email.parser import Parser
 from email.policy import SMTPUTF8
 from smtplib import SMTP
@@ -85,11 +85,11 @@ class MailHandler:
         smtp = SMTP(POSTFIX_SERVER, 25)
         msg = Parser(policy=SMTPUTF8).parsestr(message_data)
 
+        rcpt_to = envelope.rcpt_tos[0].lower()
+
         # Reply case
         # reply+ or ra+ (reverse-alias) prefix
-        if envelope.rcpt_tos[0].startswith("reply+") or envelope.rcpt_tos[0].startswith(
-            "ra+"
-        ):
+        if rcpt_to.startswith("reply+") or rcpt_to.startswith("ra+"):
             LOG.debug("Reply phase")
             app = new_app()
 
@@ -102,9 +102,9 @@ class MailHandler:
             with app.app_context():
                 return self.handle_forward(envelope, smtp, msg)
 
-    def handle_forward(self, envelope, smtp: SMTP, msg: EmailMessage) -> str:
+    def handle_forward(self, envelope, smtp: SMTP, msg: Message) -> str:
         """return *status_code message*"""
-        alias = envelope.rcpt_tos[0]  # alias@SL
+        alias = envelope.rcpt_tos[0].lower()  # alias@SL
 
         gen_email = GenEmail.get_by(email=alias)
         if not gen_email:
@@ -212,8 +212,8 @@ class MailHandler:
         db.session.commit()
         return "250 Message accepted for delivery"
 
-    def handle_reply(self, envelope, smtp: SMTP, msg: EmailMessage) -> str:
-        reply_email = envelope.rcpt_tos[0]
+    def handle_reply(self, envelope, smtp: SMTP, msg: Message) -> str:
+        reply_email = envelope.rcpt_tos[0].lower()
 
         # reply_email must end with EMAIL_DOMAIN
         if not reply_email.endswith(EMAIL_DOMAIN):
@@ -230,7 +230,7 @@ class MailHandler:
                 return "550 alias unknown by SimpleLogin"
 
         user_email = forward_email.gen_email.user.email
-        if envelope.mail_from != user_email:
+        if envelope.mail_from.lower() != user_email.lower():
             LOG.error(
                 f"Reply email can only be used by user email. Actual mail_from: %s. User email %s",
                 envelope.mail_from,
@@ -293,7 +293,7 @@ class MailHandler:
         return "250 Message accepted for delivery"
 
 
-def add_or_replace_header(msg: EmailMessage, header: str, value: str):
+def add_or_replace_header(msg: Message, header: str, value: str):
     try:
         msg.add_header(header, value)
     except ValueError: