• 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.

Trouble-Shooting and Support

Please note that 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, our recommendation is to temporarily disable add-ons to see if the problem clears up for you.

Postbox does not support the functionality of 3rd part 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.


The following add-ons are for Postbox 3 and Postbox 4.

Cloud File Sharing Add-on 1.0.1PostboxShare links to your Dropbox, Box, and OneDrive files instead of mailing the files themselves. Only available for Postbox 4.Download
Vacuum PostboxPostboxAdds a "Tools | Indexing | Vacuum..." menu item which allows you to vacuum your Postbox index to reclaim disk space and improve performance.Download
LightningMozilla Calendar TeamManage your daily schedule directly within Postbox.Download
Provider for Google CalendarPhilipp KewischAllows bidirectional access to Google Calendar.Download
Zonio 3e CalendarZonioSchedule meetings directly from your calendar without a lot of phone calls, emails or clicking in the polls.Download
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 Mac OS X.Download for Mac OS X
MyPhoneExplorerFJ Software DevelopmentMyPhoneExplorer will bring Postbox and your Android Smartphone together. With MyPhoneExplorer you can sync your contacts, calendar and task list with every android powered device.Download
ImportExportToolskaosmosImport and Export Messages.Download
QuickFiltersAxel GrudeQuickly generate mail filters on the fly, by dragging and dropping mails and analyzing their attributes. Download
Enigmail 1.2The Enigmail TeamSend and receive signed and encrypted messages using OpenPGP provided by GnuPG. You also need to install GnuPG.Download for Mac OS X Download for Windows
MinimizeToTray RevivedNils MaierMinimizes Postbox to the system tray on Windows.Download
SmartTemplate4SmartTemplate4SmartTemplate4 offers an easy way to automatically create customized replies by auto-inserting various mail headers. Download
ThunderBrowseGS! NetworksAdds browsing functions to Postbox, allowing you to be able to view websites without having to open another application.Download
MailHopsAndrew Van Tassel MailHops maps the route an email took to get to you.Download
Send LaterJonathan KamensTrue "Send Later" functionality to schedule the time for sending an email.Download
Zombie Keys (Multilanguage Keyboard)Axel Grude, Kai BolayEnter European languages (which include diacritics (accented characters, diaeresis, umlauts, etc.), ligatures, the Euro sign, etc.) into Postbox using an English keyboard. Download
QuickPasswordsAxel GrudeThis simply puts the password where you need it - the login form or your clipboard.Download
QuickFoldersAxel Grude, Alexander MalfaitOpen your favorite folders as tabs. Open folders and sub folders, move mails without scrolling around or searching. Download
WiseStampThe WiseStamp TeamShare your Social profiles and information you care about in your email signatures.Download
ReplyWithHeader Jeevanandam M.Completely manages and enables the feature of ‘Message Attribution’ for Reply, Reply All & Forward in Postbox.Download

Developer Resources

Here are a few resources that you may find helpful to your porting efforts: