You can easily fix Outlook OST Synchronization Error 8004011D-526-80040115 by using eSoftTools OST Recovery software. which helps to recover and convert OST files into PST with all email Items, for emails, notes, contacts, calendars, drafts, tasks, journals, attachments, etc. This Converter tool also provides a complete preview of all OST files items like- emails, contacts, calendars, tasks, notes, inbox items, outbox items, or other items. A free OST to PST Converter version is also available in which users can export the first 25 items.
Read More:- Fix Outlook OST Synchronization Error

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Following Fixtures Can be Applied to Fix Error 8004011D-526-80040115
You should wait till the Exchange server comes online again and resynchronize your OST file.
Check your network issues and if everything is fine then trying to resynchronize your OST file.
Sometimes recreating the profile will help you to fix the error of OST file and various synchronization issues.
Check Outlook profile settings and make sure that the default delivery destination is correct.
Run the OST Integrity check tool to diagnose different synchronization issues
You can uninstall the anti-virus software which will fix the different error of OST file.
Hope this helps you, J Wick