Outlook.com / Hotmail Mailbox Full? Here's the Fix

Outlook.com (the modern name for what used to be Hotmail) gives free accounts 15 GB of storage, shared with OneDrive. When you fill it up, incoming mail bounces and you'll see storage warnings in the web interface and in Outlook desktop or mobile apps. Microsoft's own fix is to sell you more storage through a Microsoft 365 subscription — but if you'd rather actually solve the problem instead of renting more space indefinitely, here's the full picture.

1. Check where your storage actually went

In Outlook.com, go to Settings → General → Storage to see a breakdown between Mail and OneDrive. If OneDrive is the bigger consumer, clearing out mail won't help much — you'll want to deal with OneDrive files separately. If Mail is the bulk of it, attachments are almost always the reason, not the text of the emails themselves.

2. Empty Deleted Items and Junk Email

Like most providers, Outlook.com keeps deleted messages in the Deleted Items folder until you empty it, and they still count against your quota until you do. Right-click Deleted Items and Junk Email in the folder list and choose "Empty folder" to reclaim that space immediately.

3. Sort by size and clear out attachment-heavy old mail

Use Outlook.com's search with hasattachments:yes and sort by size to find your biggest emails. A handful of years-old emails with large attachments — PDFs, videos, disk images — typically account for far more space than thousands of short text emails combined.

4. Consider whether you actually need Microsoft 365

Microsoft 365 Basic starts at a low monthly price and bundles 100 GB of storage with Office apps, which can be worthwhile if you already want the apps. But if you're only buying it to fix a full mailbox, you're paying an ongoing fee to delay a problem that will return once the new, larger quota fills up too.

5. Archive locally, then delete from the server

The approach that actually breaks the cycle: download a copy of the old emails you want to keep to your own computer, confirm the copy is complete, then delete those emails from Outlook.com. Your mailbox quota frees up permanently, and you keep every message, searchable and accessible offline, with no recurring storage fee attached to keeping your history.

Outlook.com and Hotmail both support IMAP, so any IMAP-based archiving tool can do this. MailVault is a free, open-source option for macOS and Linux: connect your Outlook.com or Hotmail account with Microsoft's OAuth sign-in (no password fiddling), select the folders you want, and MailVault downloads each message as an individual .eml file on your disk, organized in a standard Maildir structure. Once you've verified the archive — open a few emails, check attachments, search for something you remember — you can safely delete the originals from Outlook.com and get your quota back.

Manual archiving is free and unlimited in MailVault. If you'd rather it run automatically on a schedule instead of archiving in batches, that's a $4/month or $25/year premium feature — 14-day free trial on the yearly plan.

Frequently Asked Questions

Related reading: what to do when Gmail storage is full, how to free up email storage, and what to look for in an IMAP backup tool.