Filelink for Large Attachments

Many email servers do not accept messages with large file attachments. The file size restriction varies depending on the mail server configuration. While you might be able to send a message with a large attachment, the receiving mail server might refuse to accept a message with a large attachment. This is all beyond the control of Thunderbird.

Thunderbird Filelink eliminates this problem by providing support for online storage services. It allows you to upload attachments to an online storage service and then replaces the attachment in the message with a link. The message recipient clicks the link to download the attachment. As additional benefits, sending and receiving large files is much faster and both you and the recipient will save disk space.

Note that you can use Thunderbird Filelink in addition to conventional attachments. For example, you can attach small files directly to a message and use Filelink for large attachments in the same message.

The instructions below show how to configure and use Filelink with the Box online storage provider. We have an agreement with them to integrate their services into Thunderbird as well. (We used to have an agreement with Hightail, formerly YouSendIt). However, the community has been active in adding other providers through the use of add-ons with FileRun, hubiC, Mega, ownCloud-based services, Pydio (formerly AjaXplorer), Synnefo, and ~okeanos currently having add-ons.


Configuring Filelink

To use Filelink, you must first create a new account (or configure an existing account) with an online storage service provider.

  1. At the top of the Thunderbird window, click the Tools menu and select Options, or click the menu button New Fx Menu and choose Options.
  2. Select the Attachments panel and choose the Outgoing tab.
  3. Click the Add button. The Set up Filelink panel will open.
  4. Select the desired service provider from the drop-down list.
    • Choose Box, click Set up Account, or click the Get a Box account… link to create a new account.
      1. Click Set up Account to continue.

      If you are creating a new account, a browser window will open that displays the service provider’s registration page. Create an account as instructed. The service provider will send you a validation email message. Click the validation link in the message to activate your account. Enter your username (your email address) in the dialog shown above and enter your password when prompted.

      In the main configuration dialog, check Offer to share for files larger than and specify a file size (in megabytes) if you want Thunderbird to prompt you to use Filelink when a message attachment exceeds the specified size.

      Using Filelink

      When you attach a file to a message and the file size exceeds the size you have specified above, Thunderbird will automatically offer you the use of Filelink:


      To force a file to be attached using Filelink (rather than relying on Thunderbird to determine if the attached file exceeds the specified size), you can click the down arrow next to the Attachbutton on the message toolbar to access the Filelink menu option.

      Click the Link button to upload the file to the online storage service provider. (Alternatively click Ignore to attach the file as a conventional attachment.)

      When you select Link the displayed message will update to:


      When the linking is complete – that is your attachment has been uploaded to the service provider – your email will be modified and a block of text and a link will be added to the body of your email as shown below:


      Note: The message will appear in plain text, if Compose messages in HTML format is turned off in Account Settings.

      When the recipients receive the message, they will see the same information and clicking the link in the message will take them to a download page to download the attachment.