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I cannot install the plugin for PostBox


I have downloaded the file which has a .xpi file extension. I have tried everything I know but cannot get the plugin installed. I have the gmail plugin and that works fine.

Please tell me how I can install it on my mac.


All responses

Brendon Wadey  staff
Replied on Feb 26, 2014 - 13:42 UTC

Hi Mark,

Please open Postbox, click on Tools, then Addons. There will be a small gear icon in the top right corner of that pop-up, click this and choose "Install Addon From File". This will allow you to browse to the XPI file you downloaded, choose it and click OK.

Postbox will then want to restart, and it will be added.


Replied on Feb 26, 2014 - 13:44 UTC

Thanks Brendon - all done :-)

Replied on Feb 26, 2014 - 16:59 UTC

I had the same problem. Brendon, your instructions for resolving the issue work perfectly. Thank you. I suggest you place a link to installation instructions on the download page. If you click on the downloaded file all it does is open Firefox and lead you to a dead end. Steps for installation should definitely be clarified. Thanks for a great app.

Andrew  premium
Replied on Oct 30, 2014 - 23:47 UTC

Thanks for the instructions. Didn't even know Postbox had addons.

Grant Anderson
Replied on Nov 05, 2014 - 17:11 UTC

Windows 7 with Postbox.

Extension install for ToDoist in Postbox from website not working?

At http://todoist.com/postbox I try Install the App from the "Get The App - It's Free" link and it downloads a Zip File "ToDoIst_for_Postbox". (Won't "open". It will only download this ZIP file)

When you expand this ZIP file, the only file that looks like an Installation File is the "Install.rdf" file. This .rdf file is not recognized by Postbox as an Extension. There is also a "Chrome" and "Defaults" Folder(s) that don't seem to contain any kind of Extension File that Postbox recognizes. I used the method mentioned above by Brendon.

So either the file associated with the link above is broken, or ???



Brendon Wadey  staff
Replied on Nov 05, 2014 - 17:14 UTC


Your browser may be doing something to downloads. I just clicked that link and all it downloaded was an XPI file. Please try clearing cache and re-downloading.


Grant Anderson
Replied on Nov 05, 2014 - 17:42 UTC

Hi Brendon... That did it. Cleared Cache (Firefox) and it downloaded as an XPI. Many thanks...

Shawn Young  premium
Replied on Mar 08, 2015 - 03:32 UTC

I've followed your instructions but still get an error message that says, "Postbox can only use the system dictionaries installed on your Mac."

Any advice?

Galina Skovorodnikova  staff
Replied on Mar 08, 2015 - 04:28 UTC

Hi Shawn,

Sorry to hear you are having this issue. Have you downloaded the xpi file from here: todoist.com/postbox?

Do you get this error message when you select "Install Add-on From File" in the Postbox?