Send Later Version History

25 versions

Be careful with old versions!

These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.

Version 4.2.3 150.5 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Add a workaround for a Thunderbird / Postbox bug which occasionally causes Send Later to send messages multiple times.

Version 4.2.3beta1 149.8 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Try to prevent Send Later from resending scheduled messages over and over when the Drafts or Outbox is corrupted, and display a warning to the user to repair the Drafts folder and Outbox to fix the problem.

Version 4.2.2 149.5 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Fix compatibility with old Thunderbird versions. Sorry about that!

Version 4.2.1 149.5 KB Works with SeaMonkey 2.21a1 and later, Thunderbird 24.0a1 and later

Compatibility with Thunderbird 26+, SeaMonkey 2.23+.

Dutch and Finnish translation updates (thank you to my translators!). NOTE: I need a new translator for Traditional Chinese (zh-TW). If you're interested in helping out, please let me know (email! Thanks!

Fix home page URL.

Version 4.2.1beta1 149.3 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Dutch and Finnish translation updates.

Version 4.2.0 149.0 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Changes since 4.1.7:

When the user clicks on the "Put in Outbox" button, a warning now pops up explaining what that button does and why the user might actually want to click on the "Send around" button instead. There is a check-box in this pop-up to prevent it from being displayed in the future. The purpose of this new warning is to help alleviate the confusion from which some users suffer about which button to click to schedule a message.

New Armenian translation. Thanks to HrantOhanyan from BabelZilla!

Version 4.1.8beta1 146.2 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Armenian translation, thanks to HrantOhanyan from BabelZilla.

Version 4.1.7 141.0 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

  • Traditional Chinese (zh-TW) translation from Mike. Thanks to Mike and all my other translators!
  • Updated date-parsing code (version 1.3.8 of SugarJS), including some improvements to French date parsing.
  • Postbox compatibility updates; Send Later now requires Postbox 3.0.6 or newer.
  • Update compatibility range for SeaMonkey and Thunderbird.

Version 4.1.7beta2 141.0 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

New traditional Chinese (zh-TW) translation from Mike.

Version 4.1.6 139.9 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Compatibility with Thunderbird 20+.

Version 4.1.5 139.2 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Hebrew translation from Shai65 at BabelZilla. Thanks, Shai! Note: Hebrew date-parsing doesn't work yet, so all you Hebrew users will still need to type your dates in English.

New version of SugarJS with updates to date-parsing.

Version 4.1.4 134.0 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Bug fix: Fix the Dutch, Finnish and Swedish translations to reflect the fact that the check interval preference is now minutes rather than milliseconds. I'm not sure how updating these particular translations got overlooked when this functionality change was made. Sorry!

Enhancement: When Thunderbird encounters an error sending unsent messages (i.e., delivering messages from the Outbox after Send Later has put them there), log the error in the error console, to assist in debugging what is causing it (which, to be clear, is a Thunderbird problem, not a Send Later problem).

Enhancement: Update the Swedish translation.

Enhancement: Update the URL of the user guide in error messages (the old URL works but is deprecated). Also, add the user guide URL to a Finnish error message that was missing it.

Non-functional: In the source code for the add-on, comment out a function that is only used during testing so that the add-on validator on doesn't complain about it.

Version 4.1.3 134.0 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Bug fix: A bug was introduced in version 4.1.2 which caused recurring messages to fail to be rescheduled after being sent. If you use recurring messages, check to see if any of them have disappeared from your Drafts folder, and if so, put them back by copying them from Sent Items and rescheduling them!

Enhancement: Add access keys for the "Put in Outbox" button in the prompt window. You can now type Alt-O (or the equivalent in other languages) to activate the button.

Bug fix: Dynamic recurrence functions should be able to return Date objects, not just numbers of minutes.

Version 4.1.2 133.7 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Fix bug introduced in version 4.0.7: Don't send scheduled messages twice!

Bug fix: The scheduled send time was not being calculated properly when it was entered using the date and time pickers, and the keyboard rather than the mouse was used to change their values.

Enhancement: Dynamic shortcuts can now implement recurrence! See

Enhancement: Make explanatory text appear inside the text box in the "Customize Toolbar" window so that it's clearer that the text box is for Send Later.

Bug fix: In rare cases Send Later was failing to notice scheduled drafts.

Bug fix: Various date parsing improvements from Andrew Plummer, the author of SugarJS, the date parsing library used by Send Later.

Bug fix: Don't cause "Error Copying Message to Drafts Folder" when hitting Ctrl-Enter in the text box in the pop-up window, or when clicking on the shortcut buttons in the toolbar.

Bug fix: Do not allow Enter or Ctrl-Enter to work when valid time has not been entered.

Enhancement: Dynamic shortcut buttons can now return a Date object rather than the number of minutes into the future.

Bug fix (non-functional): Use closures instead of script fragments for event listeners, as suggested by AMO editors. See

Version 4.0.6 130.7 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

NOTE: If you had Send Later in your compose window toolbar prior to this release, you will have to add it back. The toolbar customization mechanism has changed in this release. It’s better now, but it’s incompatible with the old mechanism. See the user guide for details.

Enhancement: Change the add-on's name from "Send Later 3" to "Send Later", translated for every supported language. The add-on was previously named "Send Later 3" because there was an old "Send Later" add-on with similar functionality for old Thunderbird versions, but that add-on has not been maintained for years and is no longer even available on, so it is time to take its place.

Enhancement: Add back the ability to choose the date and time using the mouse using date and time pickers, instead of or in addition to use free-form text input.

Enhancement: Each of the add-on's compose window toolbar items can now be added and positioned separately, giving the user complete control over the items appearing in the toolbar. Furthermore, the user can choose whether to put free-form text input, date/time pickers, or both in the toolbar.

Enhancement: Since the shortcut buttons are now added or removed by customizing the compose window toolbar directly, there are no longer checkboxes in the add-on's preferences controlling whether the buttons appear in the toolbar.

Enhancement: Change the "SENDLATER3" status tag at the bottom of the main Thunderbird window to match the add-on's name in every language.

Enhancement: Add a Chinese description to the install manifest, so that the description that shows up in Tools | Add-ons for Chinese users will be in their native language.

Bug fix: The Send Later button in the pop-up prompt window is now activated, as it should be, when the window first comes up when re-scheduling a previously scheduled draft.

Bug fix: Prepopulating the scheduled send time when editing a previously scheduled message was not working in some circumstances.

Bug fix: The schedule button in the toolbar was not always being updated properly with the scheduled send time.

Enhancement: Improvements to Dutch date parsing.

Bug fix: If user has OS configured with custom date format, then sometimes the prepopulated scheduled send time inserted when editing a previously scheduled message is not understood by Send Later 3!

Bug fix: Add missing space after typo in error message.

Version 4.0.4 132.1 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

Enhancement: Add Dutch date parsing.

Bug fix: Some users have been seeing "Drafts folder may be corrupt" errors repeatedly, even after repairing all of their Drafts folders.

Bug fix: In recent (not yet released to the general public) versions of Thunderbird and SeaMonkey, displaying the release notes after updating the add-on was not working properly.

Bug fix: When editing a previously scheduled recurring message, the text box and button in the toolbar are supposed to be disabled because recurring messages can only be scheduled from the pop-up dialog. However, they were not being disabled as they should have been. This is now fixed.

Bug fix: In recent (probably not yet released to the general public) versions of Thuderbird and SeaMonkey, when the user edited a previously scheduled draft and then immediately tried to close the message compose window without actually making any changes to the draft, Thunderbird was asking the user whether to save the draft, even though it was unmodified and didn't need saving.

Version 4.0.3 131.1 KB Works with SeaMonkey 2.9 and later, Thunderbird 8.0a1 and later

I am very excited to announce release 4.0.3 of Send Later 3!

This release includes four major enhancements which have been requested by users more than any others.

Before describing the changes in this release, I want to give a huge shout-out to Andrew Plummer, the maintainer of the SugarJS library upon which much of the functionality in the new release depends. I also want to give a huge round of applause to my translators who have helped to make this release great. They are:

  • Dtrieb from BabelZilla (de)
  • Erwin D. Glockner (de)
  • urko from BabelZilla (es-ES)
  • Samtron-Translations (fi-FI)
  • Bigpapa from BabelZilla (fr)
  • Cesare from BabelZilla (it-IT)
  • Amigomr from BabelZilla (ja-JP)
  • markh from BabelZilla (nl)
  • Maciej Kobuszewski (pl)
  • Mikael Hiort af Ornäs (sv-SE)
  • Wang.H.K from BabelZilla (zh-CN)

Free-form date/time entry

The date and time for scheduling a message are no longer entered using clunky drop-downs. Instead, you just type in the date and time you want, and Send Later 3 parses what you typed and figures out what you meant.

Date parsing is currently supported in the following languages: English, French, German, Italian, Spanish, Portuguese, Swedish, Russian, Polish, Japanese, Korean, Simplified Chinese, and Traditional Chinese (contact me about adding support for additional languages). The add-on first attempts to parse dates using the language indicated by your locale, and if that fails, it falls back on English.

Date parsing understands all sorts of interesting syntaxes in addition to conventional date/time entry. For example, "the day after tomorrow", "next Thursday at 15:00", "the beginning of next week", etc. Date parsing in Send Later 3 is provided by the most excellent SugarJS library, created and maintained by Andrew Plummer.

Because such interesting date syntaxes can be ambiguous, Send Later 3 tells you what it thinks you meant by parsing your text in real-time and showing in the send button when the message will be sent.

This new functionality also makes it easier to schedule multiple messages at the same time, something which has been frequently requested. Rather than being forced to painstakingly selected the same values in the drop-downs over and over, you can simply copy the desired date/time into your clipboard and paste it into the date/time entry field of each message. Add the field to your toolbar to make it even faster!

Enhanced recurring messages

When scheduling a recurring message, you can now indicate a count in addition to a unit. In other words, whereas before you could specify only daily, weekly, monthly or yearly, now you can specify every 3 days, every 5 weeks, etc.

Furthermore, you can schedule monthly messages on the same week and day of every month, e.g., "the third Tuesday of the month."

SeaMonkey support

Send Later 3 now supports SeaMonkey!

Support for the Mail Merge add-on

Starting with its version 3.4.0, the Mail Merge add-on supports Send Later 3! Instructions for using Mail Merge with Send Later 3 can be found here.

(Note: Just to be clear, support for Send Later 3 in Mail Merge required changes to Mail Merge, ​not​ changes in Send Later 3. I'm not trying to take credit for the most excellent work of the author of the Mail merge add-on; I'm just letting people know that you can now use Mail Merge with Send Later 3.)

Other changes

In addition to the major enhancements described above, there are also a number of other changes in this release:

  • There is a bug in Thunderbird 15 that breaks Send Later 3. This release includes a workaround for the bug.
  • The "Send Later" column now displays properly in the unified Drafts folder.
  • The color changes to the Send Later 3 pop-up window, which a number of people described as "garish" and did not care for, have been removed. These are no longer necessary now that the UI has been simplified and made clearer in other ways.
  • The preference for controlling how often to check for messages whose scheduled send time has arrived has been changed from milliseconds to minutes, which makes a heck of a lot more sense.
  • The pop-up window that requests donations for Send Later 3 has been changed so that it no longer has the potential to cause Thunderbird to hang on some platforms. This hang is due to a Thunderbird bug, not a bug in Send Later 3, but since the Thunderbird bug has not yet been fixed, it is important to work around it in the add-on.
  • A bug which was causing recurring messages to be marked unread in the Drafts folder has been fixed.
  • A workaround has been introduced in the code which should reduce the frequency of Send Later 3 complaining about a corrupt Drafts folder, specially when using POP3 or local folders.
  • Send Later 3 now replaces the message ID in outgoing messages so that it does not inadvertently send multiple, different messages with the same message ID (relevant for both recurring messages and messages scheduled from templates).
  • Send Later 3 now correctly expands mailing lists (from your address book) before scheduled messages are saved in the Drafts folder.
  • A hidden preference extensions.sendlater3.logging.filter has been added to optionally specify a regular expression indicating which messages should be logged.

Version 3.3.10 99.3 KB Works with Thunderbird 2.0 and later


The next version to be released after this one will include significant new functionality which cannot be implemented within Thunderbird 2 or Postbox 2. Users who do not wish to upgrade to a newer version of Thunderbird or Postbox may continue to use this version as-is, but there will be no further bug-fix or feature releases compatible with Thunderbird 2 or Postbox 2.

Version 3.3.9 99.3 KB Works with Thunderbird 2.0 and later

Changes since 3.3.8:
  • Fix sorting of Drafts folders by the Send later column.
  • Another attempt to fix display of drop-down menus in compose toolbar on Thunderbird 2 on non-Linux platforms. I'm can't be certain the fix in version 3.3.8 was correct, because I can't reproduce the issue and haven't gotten feedback from anyone in the field one way or the other, but this new version of the fix should be more robust.

Version 3.3.8 100.4 KB Works with Thunderbird 2.0 and later

  • Change the label on the "Passthrough to Send Later" button to "Put in Outbox" and change its tooltip to be clearer as well. This is an attempt to fix the most common usage error people experience with this add-on, which is clicking this button when they should be clicking "Send Later at time(s) specified above". Thank you very much to the Send Later 3 translators who assisted with this change!
  • Change the font sizes and colors in the Send Later 3 dialog to make the primary functionality group clearer and attract the eye better, primarily to help people avoid clicking the "Put in Outbox" button when they should be clicking "Send Later at time(s) specified above".
  • Fix the display of the drop-down menus in the compose toolbar on Thunderbird 2 on platforms other than Linux.
  • Add a missing tooltip for the Send Later button in the compose toolbar on Thunderbird 2.
  • When displaying the release notes, scroll directly to the release notes for the version of the add-on that the user has installed.
  • When asking the user to make a donation, make the request before sending the message rather than afterward, because otherwise on some platforms, e.g., Mac OS X, the donation request window disappears when the compose window is dismissed.
  • New Simplified Chinese translation from yfdyh000 at BabelZilla.
  • The French and Dutch translations have been updated slightly as well as moved to a different location within the innards of the add-on. If you use one of these translations, you might notice that some of the strings have changed, but otherwise they should continue to work just fine. If they don't, please let me know.Compatible up to Thunderbird 15.0a1.
  • (non-functional change) Remove unnecessary, empty translation string "separator.label".
  • (non-functional change) Hard-code emacs coding-system into ambiguous files to avoid inadvertently saving them with the wrong coding system.

Version 3.3.7 95.2 KB Works with Thunderbird 2.0 and later

I need more beta testers! Several bugs introduced in the previous version of the add-on were not discovered before release because I did not encounter them myself and my pool of beta testers is not large or diverse enough. I do my best to test new versions thoroughly, but I can miss things, so the more people I have testing new versions with me, the more likely it is that they will work for everyone. I fix problems discovered by beta testers very quickly, and if you do encounter a problem, you can always revert to the previous non-beta version until I am able to fix it. So please, help make Send Later 3 better for everyone by signing up as a beta tester! See the user guide for more information if you're interested. Thank you.

Changes since 3.3.6:
  • Fix a bug introduced in version 3.3.6 when I updated the internal identifiers used in various components of the add-on as requested by the editors. This bug was causing the scheduling pop-up to sometimes fail to schedule messages properly, as well as causing the scheduled send time to sometimes fail to display for scheduled messages.
  • Fix a couple of coding errors introduced in 3.3.6 when the add-on's code was restructured to fix negative interactions with other add-ons. These coding errors don't affect recent versions of Thunderbird but do affect Thunderbird 2 and perhaps some intervening versions as well.
  • Add a new hidden preference, extensions.sendlater3.send_while_offline. This preference is currently set to true by default. It can be changed using the advanced configuration editor.
    When this preference is true and the scheduled delivery time of a message arrives while Thunderbird is in offline mode, the message is moved into the Outbox and timestamped as of that time. When it is eventually delivered after you go online, the Date in the sent message will therefore correspond to its scheduled send time. As already noted, this is the default behavior and consistent with previous versions of the add-on.
    On the other hand, when this preference is false, messages whose scheduled delivery times have passed will not be moved into Outbox and timestamped until you go back online, which means the Date in the sent message will be when you went back online, not when the message was scheduled to be sent.
    I am interested in hearing from users which of these two behaviors you think is more correct, so that I can determine which should be the default and whether the setting should be visible in the preferences dialog. Please email me ( and let me know what you think.
  • Add a Finnish translation. Than you to Samtron-Translations!
  • Add the Japanese translation to the install manifest so the add-on's description is displayed in Japanese (for Japanese users) in the add-on manager.
  • Compatible up to Thunderbird 14.0a1.
  • Add some debugging code to help me figure out why one user is seeing the scheduling pop-up when he clicks the "Send" button when he shouldn't be.

Version 3.3.5 90.1 KB Works with Thunderbird 2.0 and later

Changes since version 3.3.4:
  • The “Send Later” button that shows up when you compose a message while working offline should pop up the Send Later 3 dialog.
  • Fix a slow memory leak caused by a typographical error in a module uninitialization function.

Version 3.3.4 90.1 KB Works with Thunderbird 2.0 and later

Changes since 3.3.3:
  • Make sorting by the "Send Later" column in Drafts folders work properly.
  • Add error checking for a rarely encountered error when one of the user's Drafts folders is corrupt.
  • Remove the version number of the add-on from the message that displays at the bottom of the screen briefly when Thunderbird starts up. It doesn’t serve any useful purpose there and was forcing me to update two different files in the add-on every time I released a new version.
  • Translation updates. Thanks as always to my translators!
  • Compatible up to Thunderbird 13.0a1.

Version 3.3.3 90.1 KB Works with Thunderbird 2.0 and later

  1. Add an accelerator key for the Send Now button in the pop-up dialog.
  2. Add a preference to allow the Send Later pop-up to be bound to Alt-Shift-Enter instead of Ctrl-Shift-Enter, preserving the default behavior for Ctrl-Shift-Enter.
  3. Compatible up to Thunderbird 12.0a1.

Version 3.3.2 89.1 KB Works with Thunderbird 2.0 and later

Changes since version 3.3.1:
  • Support Postbox 3.
  • Fix bug: If you edited a previously scheduled draft, and then later composed a new message, it was possible for the default scheduled delivery time in the compose window to be initialized to the scheduled time for the previously edited draft, rather than to the current time.
  • Fix bug: The add-on is supposed to remove the scheduled send time from any draft you edit, when you start editing it, to avoid it accidentally being sent out while you were editing it. This functionality was not working properly for drafts that were followups or replies.
  • Fix release notes display to account for recent changes to Thunderbird internals.
  • Compatible up to Thunderbird 11.0a1.
  • Change some internal identifiers (not user-visible) to confirm to new coding standards for