How to add an extra email to my workspace email?

[Ad2018]

I have an Unlimited Business Email plan and I use webmail for that adres. 

I have another email and for this I have Email Essentials 

How can I combine both mail adressen into 1 webmail Application?

Thanks!

Adrian

[Nate · Accepted solution]

The Workspace email can not be combined with the Office based email on the same domain.  Select which you prefer and upgrade that plan to have the appropriate number of users, and the other can be canceled.