mailaddress: firstname.lastname@uibk.ac.at
username: c703xxxx

imap: exchange.uibk.ac.at
username: c703xxxx
port: 993 	 
encryption: SSL/TLS
Authentication method: Normal Password

smtp: smtp.uibk.ac.at
username: c703xxxx
port: 465 	 
encryption: SSL/TLS
Authentication method: Normal Password

Account Settings → Composition and Adressing → edit Directories:

General Settings:

Name: 	Universität Innsbruck
Server: mailaddress.uibk.ac.at
Base DN: dc=uibk,dc=ac,dc=at
Port:	636
Bind DN: uid=cxxxxxx,ou=uibk,ou=people,dc=uibk,dc=ac,dc=at
SSL: activate

https://exchange.uibk.ac.at

see ZID config page (in german): Installation und Konfiguration von Mozilla Thunderbird

Official support is not given, neither by Mozilla nor Microsoft.

Nevertheless, there is a PlugIn called TbSync which is able to sync calendar/contacts over the Exchange ActiveSync (EAS) protocol:

Thunderbird PlugIn TbSync

History:
There is also an outdated, (almost) stable project which is offering calendar support for Thunderbird over a xpi-PlugIn:

Exchange EWS Provider v3.9.0

Stable for reading Exchange Calendar entries. It is also possible to add/update entries, but it seems like it takes some time that all data is synchronized properly. doku