Please note that add-ons are no longer supported as of Postbox 6.0. Add-ons developed by Postbox, Inc. will be added to the core Postbox product. Legacy add-ons are available here for customers who are using older versions of Postbox.


  • Download the Add-on to your computer, such as the Desktop.
  • In Postbox, go to the Tools menu and select Add-ons.
  • Click the Gear icon or button in the upper right corner, then select Install Add-on From File...
  • Browse to the location of the add-on and select it.
  • Restart Postbox.

Troubleshooting and Support

Add-ons can change the DNA of Postbox in ways that are incompatible with its default behavior. If Postbox is not operating the way you expect, then temporarily disable add-ons to see if the problem clears up for you.

Postbox does not support the functionality of 3rd party add-ons, as it is up to each developer to support the functionality of the add-ons they author. If an add-on is not working correctly, please contact the add-on developer directly.

Postbox 5 Add-ons

macOS Sharing 1.0.2Postbox, Inc.Allows content to be sent through Postbox using the macOS Share menu. Only available for Postbox 5Download  |  Instructions
70 Email Templates Every Business Needs 1.0Postbox, Inc.70 professionally written email responses that anyone can customize and use. You'll receive emails for finding a job, hiring, making introductions, reaching out to investors, sales, and more. Only available for Postbox 5Download  |  Instructions
25 Beautifully Designed Email Signatures 1.0Postbox, Inc.25 professionally designed email signatures that will present you in the best light possible. Each signature is fully customizable, and contains all the code examples you need to make a lasting impression. Only available for Postbox 5Download  |  Instructions
Cloud File Sharing Add-on 1.1.1Postbox, Inc.Share links to your Dropbox, Box, and OneDrive files instead of mailing the files themselves. Only available for Postbox 4 and 5.Download  |  Instructions
Vacuum Postbox 1.1Postbox, Inc.Adds a "Tools | Indexing | Vacuum..." menu item which allows you to vacuum your Postbox index to reclaim disk space and improve performance.Download

3rd Party Add-ons

These add-ons are not developed or supported by Postbox, Inc.

Markdown HereAdam PritchardMarkdown Here allows you to write complex email in simple text, never taking your hands off the keyboard.Download
SpamSieveC-Command SoftwareIntegrate Postbox with SpamSieve's powerful junk filtering on macOS (requires download and purchase of SpamSieve from C-Command Software).Download for macOS
ImportExportToolskaosmosImport and Export Messages.Download
Enigmail 1.2The Enigmail TeamSend and receive signed and encrypted messages using OpenPGP provided by GnuPG. You also need to install GnuPG.macOS  |  Windows
MinimizeToTray RevivedNils MaierMinimizes Postbox to the system tray on Windows.Download
MailHopsAndrew Van Tassel MailHops maps the route an email took to get to you.Download
QuickFoldersAxel Grude, Alexander MalfaitTurn your favorites into tabs - open folders and subfolders, move mails without scrolling around or searching.Download
SmartTemplate4 v1.4Axel Grude, Marky MarkSmartTemplate4 offers an easy way to automatically create customized replies by auto-inserting various mail headers. Download
Zombie KeysAxel Grude, Kai BolayThis extension implements Microsoft's Keyboard shortcuts for international characters.Download