Make sure the Deleted Items, Drafts, and Sent Items folders (and any other folders you want to access in Thunderbird) are selected and then click Subscribe.Right-click your account name and click Subscribe.This will make it less confusing if you also use webmail or another email client to access your Office 365 email. We also recommend keeping sent messages and drafts in the Sent Items and Drafts folders in webmail folders on the server.
This setting allows you to recover deleted items. We recommend that you configure your Thunderbird to move your deleted messages to the Deleted Items folder on the server (webmail).
You can obtain a free download of Thunderbird from the Mozilla website. To request access to IMAP, please submit a Help request. With IMAP you can only access your email, not your calendars, contacts, or tasks. Thunderbird lacks Exchange support so it needs to be configured for IMAP.