The More Email You Send And Receive, The Larger Your Outlook Mailbox Can Grow. Large Mailboxes Can Take Longer To Open And Search, And Many Email Providers, Including Microsoft 365, Limit The Maximum Size Of Your Mailbox. If You Receive A Message That Your Mailbox Is Over Its Size Limit, Deleting Messages And Folders Can Help, But If You Store Your Information In An Outlook Data File (.pst) Or Offline Outlook Data File (.ost), That Data File May Not Shrink In Size Automatically.
Note : If You Use A POP Account, All Of Your Email Account Information, Including Your Folders, Email Messages, Contacts, Calendar, And Task Information Is Stored In An Outlook Data File (.pst). If You Use An Microsoft 365, Exchange, IMAP, Or outlook.com Account, A Copy Of Your Mailbox Is Stored In An Offline Outlook Data File (.ost).
To Reduce The Size Of Your Outlook Data File (.pst) Or Offline Outlook Data File (.ost), You Can Manually Compact The Data File. Select Your Version Of Outlook Below To See Instructions On How To Reduce The Size Of A .pst Or .ost File.
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