You can find this section in HostBill Admin → Settings → General Settings → Mail → Outgoing mail configuration
Define if you want to send out system emails or if you want to block system from sending any emails. If the feature is disabled - it overrides all other settings.
Choose which email address will be used as a sender (in 'From' field in your emails).
Choose the type of email client.
Enter your email address.
This is used for SMTP connection. If you need to connect using specific protocol, prefix your hostname with it, eg. ssl://smtp.example.com, tls://smtp.example.com
Used for SMTP connection - access details for that email account.
Set maximum number of email notifications HostBill should send per one cron run.