When I have an e-mail with an attachment that exceeds usual limits (say 10 Mb), I upload the file to a private remote FTP server (using a simple homemade PHP upload tool), and I add the link to my e-mail message. Of course it works, but it's still a little time-consuming compared to dropping an attachment in an e-mail.

Is there any existing tool, plugin, whatever, that would let me attach files of any size to my e-mails, and automatically upload the big ones on FTP and add the link in the message ?

  • OS : Win 7, Win XP
  • Mail client : Thunderbird (I've looked into TB extensions, no luck)
  • Mail server : Mercury Mail Transport (smtp through relay)
  • Private remote FTP

I'm not afraid of a little scripting/programming, if needed, but I don't really see where to begin.


I think Tonsho is what you're looking for. But its a paid service.

Tonsho is an interesting twist to the service. Rather than uploading files yourself, you can use a normal email client such as Microsoft outlook and Thunderbird, and send your email normally. Your email will then pass through Tonsho servers and if the attachments are too large, it will automatically upload it to a server, and provide the recipient a link.

Update: It seems Thunderbird is already planning it. Its a project called BigFiles And they've targeted Thunderbird 11 to release it.

  • Tonsho looks interesting, I will test it, but I would prefer to store the files on our own ftp. Thunderbird "BigFiles" is great news, tough, the specs looks so much like what I need !
    – Fa3ien
    Jan 28 '12 at 6:59

Your best bet is to probably make a custom Thunderbird add-on. Mozilla has published resources on making an extension here: https://developer.mozilla.org/en/Building_a_Thunderbird_extension

The code for your extension would need to do the following (probably on send):

  1. Identify the size of the attachments.
  2. (Optional) If the attachments are too big, prompt the user if they want to use tho FTP upload.
  3. Once you know you need the FTP upload, copy the file to the FTP server. (For information on FTP access, look at the FireFTP add-on for Firefox)
  4. Generate a link to the uploaded file.
  5. Delete the attachment and append a link to the bottom of the email.
  6. Send the email now sans attachment.
  • Thanks for the input, I tought of making a TB extension, but that's a little more programming than what I expected. I'll give it a try, maybe.
    – Fa3ien
    Jan 28 '12 at 6:46

I would look at some of the commercial solutions. For example, the file mailer in BarracudaDrive provides some interesting features such as password protection and sending to multiple recipients.

See the following blog for more info: http://barracudadrive.net/blog/2011/08/Securely-distribute-large-files-via-emails

The File Mailer is a product integrated with the BarracudaDrive WebDAV and Web File Manager. Files of any size can be uploaded using WebDAV or the drag and drop box feature in the Web File Manager. These files can then be sent as attachments or links to individuals or to predefined lists. Files can be emailed to an unlimited amount of lists and each list can have an unlimited amount of contacts.

The File Mailer is built on top of the existing multi user Web File Manager. Users with access to the Web File Manager can email any file they have access to via the constraints set by the administrator. Users with access to the File Mailer Administrator Panel can also create and manage contact lists, manage mail jobs, view the download history, etc.

The file Mailer is useful if you require any of the following:

  • secure and encrypted distribution of any type of non tangible items.
  • distribution of files that are too big for regular email.
  • easy distribution of data to many, even a very large number of, customers/contacts.
  • tracking of the data distributed, or require verification of delivery.
  • customized data for each customer/contact in a distribution list. Data can be customized by
  • Could you summarize that blogs article a bit? we generally prefer you add more to the answer than just a link Feb 18 '12 at 0:09

The existing answers are now mostly outdated. Recent versions of Thunderbird come with built-in support for linking large attachments. They call this support "Filelink", and they describe it here:


Several backends are supported, though I would only recommend two them currently:

since those are the only ones that can be set up with a personal server. Webdav is certainly easier to set-up, as it only requires a generic Webdav server where you can write. It's the modern equivalent of an ftp server.

Dl for Thunderbird is more interesting for attachments as it generates automatically expiring links. It's a "setup and forget" solution, where you don't really have to manage space afterwards and can scale to hundreds of users.

It's also especially useful as it can generate a sort of "reverse upload" link ("grant" as they call it). If you're having trouble receiving a file, you can just generate a link and paste it in the message. When you click on it, you are granted the ability to upload a file and the link is automatically sent to you once the upload is completed.

This feature effectively doubles its usefulness for all the contacts you're trying to exchange files with.

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