0x8004060C
The mailbox is full
What it means
The mailbox or the local data file reached its size limit, so Outlook cannot store new mail.
Common causes
- A full server mailbox
- A PST file at its 50 GB limit
- Deleted items and Sent not cleaned
How to fix it
- Empty Deleted Items and the Junk folder, then archive old mail.
- Check the mailbox quota on the provider's web page.
- Move large attachments to OneDrive and send links instead.
- For a PST file, create a second data file and move old folders into it.