How to Easily Transfer Outlook Calendars to Thunderbird Email Client?

Emails are considered the best ways to communicate and people are using different email clients. One of the popular email clients among them is Outlook and Thunderbird. Outlook and Thunderbird both email clients store emails, contacts, notes, journals, calendars etc. Outlook works with PST format and Thunderbird with MBOX file format for saving emails. Sometimes, users find a need to export Outlook calendars to Thunderbird. In the following article, we are discussing cost-effective solutions to move calendars from Outlook to Thunderbird.

ICS is a standard format used by various email clients to store calendar information such as tasks, notes, journals etc. The need to export and import ICS files arises when a user switches from web-based email clients like Gmail, Yahoo etc. to desktop-based clients. In this section, we are going to discuss the conversion of Outlook ICS files to Thunderbird.

Method 1. Move MS Outlook calendars to Thunderbird using ICS format

Here, Thunderbird Lightning add-on is used to import Outlook calendar to Thunderbird. It is an add-on by Mozilla foundation used to schedule meetings, tasks, and appointments.

Follow the steps to export calendars of Outlook to Mozilla Thunderbird –

1. Open Microsoft Outlook application
2. Select Calendars
3. Go to File Menu and choose Save Calendar from the drop-down list
4. Enter a file name and select iCalendar format (.ics) in save as type. Click Save
5. Choose the calendar and hit OK button
6. Download Thunderbird Lightning from Mozilla official site
7. Go to Add-on section and configure the Lightning
8. Now, launch Thunderbird client
9. Click on the right panel and select events and tasks
10. Choose Import from the list
11. Click on Browse button and select the calendar file which you have exported from Outlook
12. Click OK

Method 2. Export calendar events from Outlook to Thunderbird using GAMMO application

The second method consists of three steps –

Step 1. Export Calendar from Outlook

1. Open Microsoft Outlook
2. Click on File tab. Select open & Export and then choose Import/Export
3. Choose Export to a file option and then click on Next option
4. Select Outlook data file (.pst) and click on Next option
5. Select Calendar and click on Next option
6. Browse a destination to save the files and provide a name to it
7. Click on Finish button

Step 2. Import PST to Gmail account

1. Download and Install GAMMO Tool on your system.
2. Launch GAMMO tool and enter the email address of your Gmail account. Click Next option
3. Check the Calendar options and hit migrate button
4. After completing the process, a message will pop up. Click Ok
5. This will import Outlook PST to your Gmail account.

Step 3. Configure Gmail account in Thunderbird

1. Enable IMAP in Gmail account
2. Open Mozilla Thunderbird
3. Create a new account box and choose email/li>
4. Enter the name, email address, and password
5. Click on the continue button
6. Enable IMAP and click manual configuration
7. Enter the settings manually


1. Incoming: imap.gmail.com/port: either 993 (SSL)
2. Outgoing: smtp.gmail.com/port: either 25 or 465
8. Click on Re-test to import Outlook calendars to Thunderbird
9. Click create account once the details are entered correctly

Time to conclude

Two easy and cost-effective solutions are there that are discussed in this article. You can choose any of the methods as per your suitability to export Outlook calendar events to Thunderbird client.