An email alias just forwards an email to another email address. You cannot send mail directly from it. If you need to send emails from it, then you would need to create the email as a separate email account instead of an alias.
Domains removed, and the new domain was added. it can take up to 2 hours for it to start working. You can also download a backup of your account before the domains were removed at https://heliohost.org/backup/
Account has been reset and a new invite was sent to your email address. you can also download a backup of your account before the reset at https://heliohost.org/backup
nlbarbershop.com has been added as your main domain. You can download a backup before the change at https://heliohost.org/backup/
The mail subdomain is reserved by the system and cannot be added, a good substitution for this would be something like mails or mail2
The answer to this question was solved on discord: https://discord.com/channels/398197622168616962/398538798994161664/1400149694918688939
Lily offers MSSQL 2017 but it will needed to be added as an addon to your Tommy account.