You can use postfix + dovecot + roundcube + spamassassin + opendkim + pigeonhole. Maximum stability. Roundcube have aliases plugin.
You can start from here: https://wiki.archlinux.org/title/Virtual_user_mail_system_with_Postfix,_Dovecot_and_Roundcube
I used lvm with SSD cache few years, but time to time I have problems with loads after reboot. If forgot about reboots all work great with LVM raid + LVM cache. Cache can be configured without raid. And you can add or remove cache in any time. Docs: https://man.archlinux.org/man/lvmcache.7