diff --git a/docker-compose.mail.yml b/docker-compose.mail.yml
index 342479f..cfabba6 100644
--- a/docker-compose.mail.yml
+++ b/docker-compose.mail.yml
@@ -4,7 +4,7 @@ services:
   mail:
     image: tvial/docker-mailserver:release-v6.2.0
     restart: unless-stopped
-    hostname: mail
+    hostname: mail # hostname and domainname may need to be commented on some platforms (e.g. ChromeOS)
     domainname: ${LDAP_DOMAIN}
     container_name: ${COMPOSE_PROJECT_NAME}_mail
     ports:
diff --git a/docker-compose.yml b/docker-compose.yml
index 2bea9ec..d4beaf9 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -257,7 +257,7 @@ services:
     image: ${docker_repo:-zokradonh}/kopano_core:${CORE_VERSION:-latest}
     read_only: true
     restart: unless-stopped
-    hostname: spooler
+    hostname: spooler # hostname and domainname may need to be commented on some platforms (e.g. ChromeOS)
     domainname: ${LDAP_DOMAIN}
     depends_on:
       - kopano_server