We have upgraded our free account to Standard for nothing?

Today we have upgraded our Free account to Standard account (annual subscription).
We have one single user and it will remain so. No extra users will be added. But we will use multiple domains with the same email id such as:
info@domain1.com (already exists)
info@domain2.com (we created this domain and all verified)

Now we cannot create info@domain2.com mail account.
How can we create this mail account?

Note: We are using these email accounts through Outlook

Waiting your urgent feedback.

Thanks.