Sometimes after updating quota from Portal it will be not directly update to Outlook. Please follow below points to update in outlook.
Firstly, adjust the mailbox size in the portal, then wait for 5-10 minutes for Exchange to pick it up on all servers. After that OWA will be fine. Outlook is another matter if you want to accelerate it seeing the new mailbox size. Outlook caches mailbox size locally with windows and can lock that value sometimes. Outlook can be forced to check the new size by performing the steps given below:
- Take Outlook out of cache mode as it locks the file size locally for a time period.
- Increase the quota in the portal to 10 GB, just for now.
- Give it 5 minutes then login to OWA to make sure the new size is correct.
- Once verified open outlook while still out of cache mode. Verify mailbox size is being picked up by Outlook.
- Put Outlook back into cache mode.