You can not setup email account for alias domain using HELM control panel. When you create a setup domain alias as seviyom1.com when user will send an email at firstname.lastname@example.org it will be redirected to main account created for main domain means at email account email@example.com. For that you need to create firstname.lastname@example.org using HELM control panel.
1) You can not configure alias email account in outlook. For e.g. email@example.com
2) You can not login in webmail of alias email account. For e.g. firstname.lastname@example.org
1) You can send emails to email@example.com.
2) You can read emails sent to firstname.lastname@example.org in email@example.com webmail account.