diff --git a/src/create_users.ts b/src/create_users.ts
index 021706a..0c0ec56 100644
--- a/src/create_users.ts
+++ b/src/create_users.ts
@@ -13,7 +13,7 @@ export async function createUsers(
 			const { user } = await redmine.users.create({
 				firstname: capitalize(sanitize(firstname)),
 				lastname: capitalize(sanitize(lastname)),
-				mail: mail,
+				mail: mail.toLowerCase(),
 				login,
 				sendCreationMail: true,
 				generatePassword: true,