Office 365 (Thunderbird) - Modify Message Settings

1. Open Thunderbird
2. Click the Menu button next to the search bar (three horizontal lines)

   

3. From the drop down menu, select Options (On a Mac, select Preferences).
4. In the pop up menu, click on the Composition tab

   

5. From this tab there are three options
6. In General you can:
• Select how messages are forwarded
• Choose how often Thunderbird will save your drafts
• Choose whether or not you want a confirmation when using a keyboard shortcut to send a message
• Choose if you want Thunderbird to notify you if an attachment may be missing
• Set Keywords to watch for missing attachments
• Change your default text or background color
• Change the default format of your email
7. In Addressing you can:
• Choose where Thunderbird looks for emails to autocomplete
• Turn off Automatically adding emails to Collected Addresses
• Have automatically added emails entered into an address book other than Collected Addresses
8. In Spelling you can
• Set Thunderbird to check spelling before sending
• Turn on or off Enable spell check as you type
• Change the default language
• Download additional dictionaries (not tested for Office 365 compatibility) 

See Also:

• Office 365 - Support for non-Microsoft clients
• Office 365 - Which clients/protocols will be supported?
• Office 365 - Exchange Online Basic Authentication Overview
• Office 365 - Set up your mobile device or desktop client