The easiest way that I have found is to use the Davmail connector.
This is a Java applet that runs in the background on your Windows 10 PC. To Thunderbird it looks like IMAP for receiving email, SMTP for sending it, and LDAP for address book queries. On the Office365 side it talks the native protocols.
I've been using it for about five years now, and IME it's solid and reliable.
The installation pre-requisite is Oracle Java. Download the JRE from the Java download page. At the time of writing the appropriate download file is jre-10.0.1_windows-x64_bin.exe
. (If you get asked to create an Oracle account, there is a small-print "Skip this step" if you know to look for it.)
Configuration settings for Davmail
Main
- Exchange protocol: Auto
- OWA (Exchange) URL: https://outlook.office365.com/EWS/Exchange.asmx
- Local IMAP port: YES 143
- Local SMTP port: YES 25
- Caldav HTTP port: YES 1080
- LDAP port: YES 389
- Trash keep delay (POP): 30
- Sent keep delay (POP): 90
- IDLE folder monitor delay (IMAP): 2
- Everything else: NO or Blank
Network
- Bind address: 127.0.0.1
- Everything else: NO or Blank
Advanced
- Edit Caldav notifications: YES (you may prefer NO)
- Display startup banner: YES
- Enable KeepAlive: YES
- Everything else: NO or Blank
Configuration settings for Thunderbird
Tools > Options > Addressing