Outlook Sent Emails Cannot Be Saved to "Sent" Folder?

I have restored my old mails but when I send mails outlook cannot save them to sent items. Whereas when I send with “thunderbird” I don’t have this problem. what is the cause of this problem?


  • It saves what I send from webmail to sent.
  • If I send from Thunderbird, it saves to sent.
  • It cannot save what I send from Outlook to sent.

Why are sent, drafts all arranged like inbox subcategories?