Microsoft offers 15 GB of email storage space per free Outlook.com account. Office 365 Home and Office 365 Personal subscribers get 50 GB of space.
If your inbox is full, you won't be able to send or receive any messages. Also, people who send you email will get an error message that your inbox is full. To make room in your inbox, try these solutions.
See how much storage you've used
You can see how much storage you've used in Settings.
Note: This feature is only available in the Outlook.com beta.
At the top of the page, select Settings > View full settings.
Select General > Storage.
Free up storage
There are a number of ways to free up storage in Outlook.com.
Empty your junk folder
Empty your Junk Email folder by right-clicking the folder and selecting Delete all.
Sweep unwanted email from your inbox
Use the Sweep button to quickly remove unwanted email from your inbox or archive folders. Sweep lets you automatically delete all incoming email from a particular sender, keep only the latest message from that sender, or delete email that's older than 10 days.
To sweep your inbox, choose a message you want to sweep, and select Sweep.
To learn more about Sweep, see Organize your inbox with Archive, Sweep, and other tools in Outlook.com.
Save attachments to OneDrive
Saving photos and documents to OneDrive is another good way to make room in your inbox.
At the top of your message list, select Filter > Sort by > Size.
Note: If the message list sorts the smallest messages on top, click Filter > Sort by > Size again to put the largest messages on top.
Select the message containing the attachments your want to upload to OneDrive.
Under the attachment, select Save to OneDrive.