How to Use Microsoft 365 Email Before Adding a Custom Domain
Question details
The user wants to know if they can send and receive emails using the default onmicrosoft.com domain before setting up a custom domain, and how mailbox limits work under their nonprofit license.
- Product
- Microsoft 365 Business Premium (Nonprofit)
- Device & OS
- not provided
- Scenario
- Setting up email communications for a nonprofit organization before a custom domain is fully registered or connected.
- Observed behavior
- The organization needs to verify email functionality with the default domain and clarify user mailbox licensing limits.
Ensure you have access to the Microsoft 365 Admin Center with global administrator or billing administrator privileges to review your nonprofit licensing terms.
Use the Default onmicrosoft.com Domain for Email
You can immediately start using Microsoft 365 email services without a custom domain by utilizing the tenant's initial domain.
When you create a Microsoft 365 tenant, you are provided with a default onmicrosoft.com domain. This domain is fully functional for Exchange Online services, meaning your staff can send and receive emails immediately while you prepare to migrate or register your organization's custom domain.
Log in to the Microsoft 365 admin center using your administrator credentials.
Navigate to 'Users' > 'Active users' and ensure your nonprofit staff have been created and assigned a primary email address ending in your initial onmicrosoft.com domain.
Verify that each active user has a Microsoft 365 Business Premium license assigned. This license includes the Exchange Online entitlement necessary to provision a mailbox.
Have a user log in to Outlook on the web using their onmicrosoft.com credentials to test sending and receiving emails.
Check Mailbox Licensing Limits with Support
Confirm exactly how many licensed mailboxes are included in your nonprofit plan to avoid service interruptions.
Looking for a cost-effective office suite for your nonprofit?
While Microsoft 365 handles your email hosting, WPS Office provides a free, lightweight, and highly compatible alternative for creating documents, spreadsheets, and presentations. It helps nonprofits save on software costs while maintaining full productivity.
Frequently Asked Questions
Can I change my initial onmicrosoft.com domain later?
Yes, you can add up to five custom onmicrosoft.com domains or connect your own organization's custom domain (e.g., your-nonprofit.org) at any time through the Microsoft 365 Admin Center under Settings > Domains.
Do all 300 users in my Business Premium plan automatically get a mailbox?
Not necessarily. While the plan may support a capacity of up to 300 users, each user must be actively assigned a license that includes an Exchange Online entitlement to successfully generate and use a mailbox.
Will emails sent to the onmicrosoft.com address still arrive after I add a custom domain?
Yes, as long as you keep the onmicrosoft.com address configured as an alias for the user, they will continue to receive emails sent to that original address even after the custom domain is set as the primary email.
Does WPS Office offer custom domain email hosting?
No, WPS Office focuses on providing a powerful, locally installed and cloud-integrated office suite for document creation and editing. You will need a dedicated email provider like Microsoft 365 or Google Workspace for custom domain email hosting.
