Incoming messages bounced, inbox overquota but appears ok?

[RCP]

Keep getting the message below, despite cleaning up all folders? Any clues?

A message was sent to you that was returned to the sender(bounced) because
it would have caused your mailbox quota to be exceeded.

The following is the reason that the message was over quota:

Quota Type: bytes in the mailbox
Quota Available: 0
Total Quota: 10485760

 

[William Lefkovics [MVP]]

Deleted Items? Sent Items?

In Outlook, you can right click on the account in the folder view (if it is
Exchange it will say something like First Name Last Name - Mailbox) and
select Properties. Then Folder Size. That will tell you the size of your
mailbox folder by folder. That should identify where the content is.

 

[Gordon]

Keep getting the message below, despite cleaning up all folders? Any
clues?

A message was sent to you that was returned to the sender(bounced) because
it would have caused your mailbox quota to be exceeded.

The following is the reason that the message was over quota:

Quota Type: bytes in the mailbox
Quota Available: 0
Total Quota: 10485760

It's referring to the mailbox at your ISP, NOT the folders on your machine.
Have you set Outlook to "keep messages on server" perhaps and not set a
time limit for them to be deleted?