diff --git a/crates/email/src/mailer.rs b/crates/email/src/mailer.rs
index 12ee5e35e..0b5f96d97 100644
--- a/crates/email/src/mailer.rs
+++ b/crates/email/src/mailer.rs
@@ -53,6 +53,8 @@ impl Mailer {
         Message::builder()
             .from(self.from.clone())
             .reply_to(self.reply_to.clone())
+            // By passing `None`, lettre generates a random message ID
+            // with a random UUID and the hostname for us
             .message_id(None)
     }