What is the size of online archive in Outlook 365?
The archiving feature in Microsoft 365 (called auto-expanding archiving) provides up to 1.5 TB of additional storage in archive mailboxes. When the storage quota in the archive mailbox is reached, Microsoft 365 automatically (and incrementally) increases the size of the archive until the archive mailbox reaches 1.5 TB.
Which is the online archive size that you get when archive just enabled in Office 365 Exchange Online for e5 subscription?
Each Exchange Online Archiving subscriber initially receives 100 GB of storage in the archive mailbox.
What is the size of online archive?

Online archive has a limit of 100GB so the storage overview page needs to extend to include the archive mailbox to show the user the size of ALL of their folders.
What is the archive mailbox storage limit for Office 365 E1?
100GB
All Business mailboxes (and E1) receive a 50GB primary mailbox + 50 GB cloud archive mailbox = 100GB total storage.
Does Office 365 E3 have unlimited archiving?
For your concern, the short answer is yes. The Office 365 E3 license indeed has unlimited archive mailboxes storage. For more details, you can view Storage limits across Office 365 options section in this article. For auto-expanding online archive storage feature, I believe there is no other limits with this feature.
Why is my Outlook still full after archiving?

After ‘archiving’, the mailbox still shows FULL and server data size does not decrease. 2.) Delete all the logs, messages and info inside these 3 folders (Conflicts, Local Failures and Server Failures). This is to allow to freshly download all the emails from Exchange Server to Email client (outlook).
Does Outlook online archive count towards quota?
Symptoms. The Archive feature is enabled on your mailbox, but the mailbox reaches its quota.
How do I clean up my online archive in Outlook?
Archiving the mailbox using Clean Up Old Items
- Open Outlook.
- Click File in the top-left corner.
- Under Info tab (1), click Tools (2)
- Choose Clean Up Old Items from the dropdown (3)