Due to a error on default postfix configuration, postfix in RHEL 10 has broken "postscreen_cache_map" and "address_verify_map" setting. https://www.reddit.com/r/AlmaLinux/comments/1nl6j8v/postfix_in_almalinux_10_has_broken_postscreen/ This causes a incorrect functioning of ISPConfig. IMHO, It would be better to set these values during ispconfig installation to "lmdb" I have fixed with: Code: postconf -e 'address_verify_map = lmdb:$data_directory/verify_cache' postconf -e 'postscreen_cache_map = lmdb:$data_directory/postscreen_cache'