Using FastMail with Mozilla Thunderbird 3.x

What you need to know

Thunderbird 3 is the latest release from the Mozilla messaging team. Thunderbird 3 offers native support for FastMail's IMAP compression algorithm to provide improved performance downloading and retrieving messages from the FastMail servers.

The screen shots in this guide are taken from an Apple Macintosh computer, but they are almost identical to the Windows version of Thunderbird.

Thunderbird is a free download available from:

Note: If you already know how to set up your client, and you already understand the information below, see this help page for the server information you need to set up your e-mail client. The Troubleshooting Issues section at the bottom of this page may be helpful if you have problems.

In order to use Mozilla Thunderbird with FastMail, you'll need to enter the following information:

  • username - When you signed up for FastMail, you chose a username which is also your e-mail address. You must use the full username, including the name and the domain part, which is the part after the '@' symbol. For example, a user named John Doe might have chosen a username of "". Make sure that you specify your username in lowercase only.
  • password - When you signed up for FastMail, you chose a password to go along with your username. You will need the password to access your account. The password also keeps others from being able to access your e-mail. Your password is case sensitive, so be sure that you type it in correctly. "PASS123" is different to  "pass123". Often, users forget about the CapsLock button and mistype their password.
  • incoming mail server (IMAP or POP) - This is the server that you get your e-mail from. Internet Message Access Protocol (IMAP) and Post Office Protocol (POP) are retrieval methods used to move e-mail messages from the server to your e-mail client so that you can read your messages. POP access is not available for all service levels, please check the pricing table for details. Secure Sockets Layer (SSL) is required for your protection as well. SSL keeps people from reading your e-mail as it is transmitted between the e-mail server and your computer.
  • outgoing mail server (SMTP) - This is the server that sends your e-mail. Simple Mail Transfer Protocol (SMTP) is the method that your client uses to move e-mail messages from your client to the server so that it can send your messages. The FastMail SMTP server is not available for all service levels, please check the pricing table for details. If your service level does not allow use of the FastMail SMTP server, you must use the SMTP server provided by your Internet Service Provider (ISP).

    The FastMail SMTP server requires SMTP Authentication. This keeps people who are not users of the FastMail service from using the SMTP server to send spam messages on the Internet. SSL is required for the FastMail SMTP server. If you don't use the FastMail SMTP server, you may have different options or requirements. You will need to get that information from your ISP.

Incoming/Outgoing Server Setup

  1. First Time Startup
    After installing Thunderbird, you will be presented with the new start-up Setup window.
    Enter your FastMail user name and password and press Continue.

  2. Fix Server Names
    Thunderbird will attempt to connect to our servers, you will need to Edit the server names and ports.

    Click the Edit button and modify the following values:
      Incoming:   Port: 993   SSL/TLS security
      Outgoing:   Port: 465   SSL/TLS security

      Also ensure your Username contains your complete FastMail username

    When finished, the window should look like the following, press the Re-test Configuration button.

    Thunderbird will test the configuration, you should see GREEN success images next to the server names.
    Click the Create Account button.

  3. Subscribe to the Server Folders
    Sometimes Thunderbird will not automatically discover all of the folders that are part of your FastMail account. It is important to ensure that Thunderbird has subscribed to all the required folders.
    Using the menu, choose File / Subscribe....

    You will want to subscribe to all your folders (especially INBOX, Junk Mail and Sent Items) listed within your FastMail account.
    Your screen should look similar to below after subscribing. Press the OK button to complete.

  4. Setup Server Folders
    Thunderbird needs to be set to utilize the FastMail Sent Items folder to save its sent messages.

    Using the menu, choose Tools / Account Settings...
    Choose Copies & Folders in the list on the left.
    Under the Sending Messages section, choose Other and choose the Sent Items folder from the FastMail account.

    When done, your window should be similar to this.

  5. Disable Thunderbird Junk Filter
    Since FastMail already has server-side junk mail filtering, you can choose to disable the junk-mail filtering within Thunderbird.

    If you do enable Junk filtering, be sure to use the Junk Mail folder on your FastMail account.
    This can be done by selecting Other and locating the Junk Mail folder from your folder list.

    When complete, you can press the OK button to save all your Account Settings changes. Thunderbird is now setup correctly to access your FastMail account!

    Your folder list in Thunderbird should appear similar to the following:

Optional: Sync your Offline Database

If you have a large amount of email stored in your FastMail account, you may want to perform the first sync now.

Using the menu, choose File / Offline / Download, Sync Now... The following window will appear. Be sure to put a Checkbox for the Mail messages.

Press the OK button and Thunderbird will download all your email to an offline database on your local hard drive.

Known Issues

Thunderbird 3.01 has a bug that causes some messages in sub-folders to be incorrectly marked as UNREAD.
The Mozilla team is aware of this issue and will hopefully issue an update soon.

Last modified on: Wed Jan 27 18:00:00 UTC 2010