Most of time Outlook OST mailbox corrupted due to virus attack. And for fix this problems users need a third party tool who help to Convert OST to PST all mailbox folders such as - Inbox, outbox, sent mail, note, task, journals, draft, calendars, appointments, contacts, deleted mail etc. The Best third party tool is Sifo OST to PST Converter software. By help of this software you save your recovery Mailbox into multiple file like EML/ HTML/ PST/ MBOX/ MHTML/ DOC/ MSG/ Office 365 etc.