diff --git a/docker-compose.yml b/docker-compose.yml
index 02832c4f..26c475e7 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -8,11 +8,14 @@ services:
     container_name: ${CONTAINER_NAME}
     env_file: mailserver.env
     # To avoid conflicts with yaml base-60 float, DO NOT remove the quotation marks.
+    # More information about the mailserver ports:
+    # https://docker-mailserver.github.io/docker-mailserver/edge/config/security/understanding-the-ports/
     ports:
-      - "25:25"
-      - "143:143"
-      - "587:587"
-      - "993:993"
+      - "25:25"    # SMTP  (explicit TLS => STARTTLS)
+      - "143:143"  # IMAP4 (explicit TLS => STARTTLS)
+      - "465:465"  # ESMTP (implicit TLS)
+      - "587:587"  # ESMTP (explicit TLS => STARTTLS)
+      - "993:993"  # IMAP4 (implicit TLS)
     volumes:
       - maildata:/var/mail
       - mailstate:/var/mail-state