Tom de Jong

Accessing Microsoft Exchange's In-Place/Online Archive through Thunderbird via DavMail

Background

The University of Nottingham offers a Microsoft Exchange email account which I accessed through Thunderbird. Recently, university IT set a new archival policy that moves any message older than 90 days into an online archive [1]. This online archive is Microsoft Exchange's In-Place Archive, sometimes also known as Online Archive, and hereafter referred to as In-Place/Online Archive.

The problem is that the In-Place/Online Archive was not accessible through Thunderbird, only through the Outlook web interface or the official Outlook application (only available on Windows/Mac). Even worse, the In-Place/Online Archive is not exportable so that I could not even get offline copies of any emails older than 90 days.

Fortunately, using the DavMail gateway I could get access to the In-Place/Online Archive in Thunderbird. The full setup is described below.

[1] https://uniofnottm.sharepoint.com/sites/DTS/SitePages/Email.aspx#view-emails-or-calendar-entries-that-are-older-than-90-days (requires sign-in)

Installing and Setting up DavMail

Install DavMail. I used the Flatpak to get version 6.5.1.

Following this comment on a DavMail GitHub issue, update the configuration file davmail.properties with the following lines. (For the Flatpak this file is in ~/.var/app/org.davmail.DavMail/config/.)

davmail.oauth.clientId=d3590ed6-52b3-4102-aeff-aad2292ab01c
davmail.oauth.redirectUri=urn:ietf:wg:oauth:2.0:oob
davmail.mode=O365Manual
-- Replace by your company's Tenant ID
davmail.oauth.tenantId=67bda7ee-fd80-41ef-ac91-358418290a1e

Now start DavMail.

Setting up Thunderbird

To add your account to Thunderbird, follow the instructions on the DavMail website. In short: add a new account with your email address and password, configure the server settings manually (incoming: IMAP, localhost:1143; outgoing: localhost:1025; both normal password and your email address as username), and follow the authentication instructions.

To get access to Microsoft Exchange's In-Place/Online Archive, we follow this StackOverflow answer and go to the Server Settings of your account, click the Advanced button and add /archive next to the Public (shared) field.
Restart Thunderbird and your In-Place/Online Archive will now appear under a new /archive folder.

Unfortunately, DavMail does not support IMAP (un)subscribe yet, so that you must sync all folders, but other than that everything works great.