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Microsoft 365 Family Mailbox Storage and Custom Email Domains Guide

Amos Gikunda Oct 15, 2026 870 views

Question details

The user wants to find out the mailbox storage capacity for shared Microsoft 365 Family accounts and if custom email domains are supported.

Microsoft 365 Family Mailbox Storage and Custom Email Domains Guide

Product: Microsoft 365 Family
Device & OS: not provided
Scenario: Planning to share a Microsoft 365 Family subscription and set up personalized email domains for family members.
Observed behavior: Seeking clarification on individual storage limits and the current status of creating new personalized-domain Outlook.com addresses.

Before you start

Log in to your Microsoft account online to verify your current subscription status and check your existing mailbox storage usage.

Solution 1Recommended

Verifying Mailbox Limits and Custom Domain Policies

Understand your allocated 50 GB mailbox storage per user and navigate the recent changes to personalized email domains in Microsoft 365.

Each person sharing a Microsoft 365 Family subscription receives a separate Outlook.com mailbox with up to 50 GB of premium storage space.

Regarding custom email domains, Microsoft updated its policy. As of November 30, 2023, Microsoft 365 subscribers can no longer create new personalized email addresses associated with an Outlook.com mailbox.

Check Storage

Access Settings

Click the Settings (gear icon) in the upper right corner of the Outlook web interface.

View Mailbox Usage

Navigate to 'General' and select 'Storage' to view your current 50 GB mailbox usage and manage your space.

Manage Domains

Go to 'Premium' and click on 'Personalized email address' in your settings to view any legacy domains you have already set up. Note that new domain setups are no longer supported.

Verifying Mailbox Limits and Custom Domain Policies

Legacy Custom Domains: If you successfully connected a personalized domain to your Outlook.com mailbox before November 30, 2023, you can continue to use it subject to Microsoft's current service policies.

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Frequently Asked Questions

Can I still use my existing custom email domain with Microsoft 365 Family?

Yes, if your personalized domain was already linked to your Outlook.com mailbox before November 30, 2023, you can continue to use it. Existing personalized addresses remain active and are subject to Microsoft’s standard service policies.

What happens if I exceed the 50 GB mailbox storage limit?

If you exceed the 50 GB Outlook.com storage limit, you will not be able to send or receive new emails until you free up space. You can do this by deleting older emails, emptying your deleted items folder, or removing large attachments.

Does my mailbox storage share space with my OneDrive storage?

Microsoft allocates 50 GB specifically for your Outlook.com mailbox. However, email attachments and inline images are also counted against your 1 TB Microsoft storage limit (OneDrive). If you run out of OneDrive space, your email capability may also be restricted.

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