Hi AndrewDuck and Traei2424851653eu,
Thank you for reaching out.
The secondary email address on the Adobe account is generally used for security or recovery. However, you can have only one Acrobat Sign account under one email address. Using a single Acrobat Sign account under two email addresses is impossible. The primary email is used as the Adobe ID and hence under the same email the Acrobat Sign account creates.
Traei2424851653eu, If you need the account for 20 users, you can check the team and business plan. For more information, refer to the following help page: https://adobe.ly/40SQhRK.
Thanks,
Meenakshi