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