diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index cc8a0950..c2399cf7 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -14,7 +14,7 @@ def postfix_dane_map(domain_name):
 
 @internal.route("/postfix/domain/<domain_name>")
 def postfix_mailbox_domain(domain_name):
-    if re.match("^\[.*\]$", domain_name):
+    if re.match(r'^\[.*\]$', domain_name):
         return flask.abort(404)
     domain = models.Domain.query.get(domain_name) or \
              models.Alternative.query.get(domain_name) or \
@@ -39,7 +39,7 @@ def postfix_alias_map(alias):
 
 @internal.route("/postfix/transport/<path:email>")
 def postfix_transport(email):
-    if email == '*' or re.match("(^|.*@)\[.*\]$", email):
+    if email == '*' or re.match(r'(^|.*@)\[.*\]$', email):
         return flask.abort(404)
     _, domain_name = models.Email.resolve_domain(email)
     relay = models.Relay.query.get(domain_name) or flask.abort(404)
diff --git a/core/admin/mailu/ui/forms.py b/core/admin/mailu/ui/forms.py
index b6c45189..798bd923 100644
--- a/core/admin/mailu/ui/forms.py
+++ b/core/admin/mailu/ui/forms.py
@@ -7,7 +7,7 @@ import flask_wtf
 import re
 import ipaddress
 
-LOCALPART_REGEX = "^[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)*$"
+LOCALPART_REGEX = r'^[a-zA-Z0-9!#$%&\'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&\'*+/=?^_`{|}~-]+)*$'
 
 class DestinationField(fields.SelectMultipleField):
     """ Allow for multiple emails selection from current user choices and