All e-mail is stored on our web servers until you download it, typically through your Outlook program.
One item to check is the 'Save on Server' setting. That should be set to one month or less. Thus, all your e-mail is backed up on the server for a month and then automatically deleted. This is also a security precaution in case your e-mail is ever hacked - the old e-mails will be gone.
If you save e-mail on the server for a longer time period, especially if some have large attachments, you will eventually fill up your mailbox allocation and will not be able to receive any more e-mails until you clean out the mail on the server. Senders will receive a Mailbox Full error in reply to any e-mails they send to you.
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