The following instructions step through the process of reconfiguring Thunderbird after being migrated from Exchange 2007 to Office 365's Exchange Online service.
On your mailbox account name, right-click then select Settings.
Click on Server Settings.
In the Server Name field, enter outlook.office365.com.
Select SSL/TLS for Connection Security and Normal Password for Authentication Method, then click Outgoing Settings in the left menu.
Check that the server settings are the following:
If the settings are correct, move to step 9.
If the settings are incorrect: with the server selected, click Edit, then move to step 8.
Adjust the settings to reflect the following:
When finished, click OK.
When prompted, enter your IdentiKey password, then click OK.
Your account will now be reconfigured.