Send Later

Thunderbird Extension

 Send Later logo

Schedule email messages to send later

Release Notes

Send Later release notes

CURRENT IMPORTANT KNOWN ISSUES

Potential Thunderbird + Send Later Drafts folder corruption with TB128+

TLDR Currently, you could lose data if you use Send Later with Thunderbird 128 or newer. There is a workaround for this issue in release 10.5.7 of Send Later, but we don't yet know for certain if this workaround works for everyone. You may wish to mitigate the risk as described below.

A bug in Thunderbird 128 or newer can corrupt Thunderbird's copy of your Drafts folder in an IMAP account when you schedule a message with Send Later. This may also happen at delivery time when you have a recurring message scheduled.

The impact of this bug is serious and includes data loss. Scheduled messages could be not sent at all, or could be sent multiples times, and unsent scheduled messages could be deleted entirely.

A good (but not perfect) test of whether this bug is impacting you is to schedule five messages with different contents with Send Later and then check all five messages in your Drafts folder and make sure all of them have the correct headers and contents. If they're all correct, you're probably safe, because for people impacted by this issue, it happens consistently enough that scheduling five messages in a row should trigger it.

As a workaround, you can stay on Thunderbird 115, or you can configure Thunderbird to store your drafts under Local Folders rather than in your IMAP account. We have not seen this issue occur with a local Drafts folder.

The Thunderbird team is actively working on finding and fixing the Thunderbird bug.

Linux, Wayland: Send Later popups are blank for TB121+

If you are using Wayland on Linux with Thunderbird newer than 121.0b5 and older than 128.3.2 or 132.0b5, the Send Later popup in the main Thunderbird window is blank. The scheduling popup in the compose window is also blank, with Send Later 10.5.5 or newer.

If you are experiencing this issue you should upgrade Thunderbird so that you're using at least 128.3.2 or 132.0b5. If you've done that and you're still experiencing this issue, please let me know.

If you can't upgrade Thunderbird for some reason, there are other available workarounds:

For some people, the scheduling popup gets narrower every time you schedule a message

We are aware of this issue but have not yet had time to fully investigate it. For some users, uninstalling and reinstalling the add-on makes the problem go away. If you are running into this issue, please add a comment to the ticket above indicating what OS and Send Later version you are using and whether uninstalling and reinstalling the add-on fixes the problem for you.

Scheduling pop-up disappears or "flies off screen"

Some users are experiencing a problem where when you try to open the scheduling popup in a compose window, it flashes briefly and then disappears or seems to fly off the screen. This appears to be a Thunderbird issue, which we are tracking here. There are several possible workarounds:

Send Later is known to have issues with Betterbird

The Send Later add-on is not regularly tested with the Thunderbird fork called Betterbird, and there are known, unresolved issues which may prevent the add-on from functioning as intended. Using Send Later with Betterbird is therefore not recommended.

Send Later may be incompatible with the "Check and Send" add-on

It has been reported to us that there are compatibility issues between the "Check and Send" add-on and Send-Later. We have not yet investigated this issue, so use the two add-ons together at your own risk.

Welcome! We've been hard at work enhancing Send Later's functionality and making it more robust and reliable, and we're excited to share our progress with you.

This page focuses on user-visible changes to Send Later. Pre-release (beta) versions aren't listed separately here; their changes are listed as part of the next public release. To see pre-releases, visit our GitHub release page.

The full Send Later user guide is available here.

We put a lot of time and effort into Send Later, and we hope that if you find it useful you will consider supporting it. See the user guide for how to do that.

Release 10.6.x

Bug fixes

Fixed in 10.6.1: The message that was previously displayed when there were scheduled message when Thunderbird is shut down incorrectly said "Send Later" in the text when it should have said "Thunderbird", which made the message confusing. It now says the right thing.

Release 10.5.x

Improvements

In Thunderbird 128 or newer, Delivery Status Notifications work for messages scheduled with Send Later 10.5.1 or newer.

In Send Later 10.5.5 or newer, when using Thunderbird 128 or newer the scheduling popup is now "attached" to the Thunderbird window by default, rather than being a separate window. There is a new "Detach scheduling popup from compose window" preference you can enable if you find that the attached scheduling popup still isn't working for you (it disappears immediately after it is opened).

Bug fixes

Fixed in 10.5.3: When the user selects one or more messages in the messages list and then uses the "Schedule message(s)" menu command, the pop-up window is now filled in properly with the default send time.

Fixed in 10.5.4: the pop-up scheduling window is now dismissed properly when the message composition window it's associated with is closed.

Fixed in 10.5.6:

Release 10.4.x

New features

None.

Improvements

Send Later now obeys the mail.sanitize_date_header Thunderbird preference. If this preference is set to true then, as with messages sent directly without Send Later, the Date header inserted into scheduled messages upon delivery will be in the UTC timezone and will always have 00 for the number of seconds.

There is a new autoUpdateDraftsFolders advanced preference which defaults to false. If you set it to true then whenever Send Later iterates through all Drafts folders it will tell Thunderbird to refresh them. You may need this if you schedule messages on one machine and have another machine deliver them; you probably won't need it otherwise. If you do enable this, you should configure Thunderbird to synchronize your Drafts folder locally because otherwise the performance impact could be noticeable, especially if you have a lot of drafts.

Translation updates.

Bug fixes

Release 10.4.3

Fixed the "Skip next occurrence" right-click menu command, which was deleting the scheduled message instead of skipping its next occurence!

The scheduling pop-up is supposed to remember the previous values when the user edits a previously scheduled message or when the user opens the pop-up, edits its contents, closes it, and opens it again. At some point this fixed. Now it's fixed.

Release 10.4.2

Fixed an issue with Thunderbird 122 and newer which was causing the Send Later dialogue not to close after scheduling a message.

Release 10.4.1

Send Later previously assumed that there could be only one "local" account in a Thunderbird profile, but it turns out that's not the case. Therefore, when we're looking for the user's outbox we need to iterate through all available local accounts rather than just assuming there's one. Otherwise Send Later might not be able to deliver scheduled messages.

Release 10.4.0

Many people reported that the Send Later scheduling window was disappearing immediately after it popped up when they clicked on the Send Later button in a compose window. This appears to be due to a bug in Thunderbird. As a workaround, the scheduling window has been modified so that it is no longer "attached" to the button and is instead a separate window which does not exhibit this problem.

We have continued to see consistency issues when editing scheduled drafts and rescheduling them, e.g., the changed content or schedule not being saved to the IMAP server, old versions of the draft continuing to appear in the Drafts folder, etc. These issues have been observed most frequently with Gmail but may also occur with other types of mail server. Two changes in Send Later have been introduced in this release to attempt to mitigate these issues:

Release 10.3.x

New features

Internal logging

Send Later now has the ability to keep an internal log in local storage that persists across Thunderbird sessions. This is very useful for debugging issues that take a long time to manifest and/or manifest at an unpredictable time so they aren't discovered right away, because in either of those cases Thunderbird may get restarted before the issue is discovered in which case the logs related to it are gone from the error console.

This adds a new "View internal log" link to the main window pop-up which opens the internal log page. Internal logging is disabled by default. It can be enabled, disabled, or cleared on the internal log page, and there's a "Copy" button on the internal log page which allows the contents of the log to be copied to the clipboard so they can be easily pasted into a file or email message.

Other new features

The list of scheduled drafts in the main window pop-up now includes the folder each draft is located in.

If Send Later discovers at delivery time that a message is too large for Thunderbird to deliver, i.e., Thunderbird is going to refuse to deliver the message if Send Later puts it in the Outbox and delivery of other messages will also be blocked, then Send Later now pops up an alert instead of putting the message into the Outbox.

Improvements

There are now column headers on the list of scheduled drafts in the main window pop-up.

When there are no scheduled drafts we know say that explicitly in the main window pop-up rather than just leaving it empty.

Translation updates.

Bug fixes

When throttleDelay is in use, message that are deleted immediately after they are sent, before the throttle delay is imposed, rather than after the delay. Otherwise if there's another issue which causes the main loop to error out before the delay is finished, we could accidentally try sending the message again in the next main loop, which will cause a bogus warning about a corrupt drafts folder.

When we fail to reschedule the next instance of a recurring message, the error message that we were popping up claimed that the original message wasn't deleted, but in fact we were deleting it. This is now fixed.

The amount of time we wait for each message to finish being delivered in the main loop is now increased if needed to match throttleDelay when it is set, to make it less likely that the throttleDelay will cause us to error out of the main loop unnecessarily.

Release 10.2.x

You can now sign up to be a beta-tester

We love our beta-testers, who get pre-release versions of Send Later before everyone else and help us find the bugs and other rough edges that we missed in our testing.

To switch to the "beta channel" and thereby become a beta-tester, do the following:

  1. Go to the GitHub releases page.
  2. Click on the title of the first listed release.
  3. Download the file "send_later_beta.xpi" from the release page. (If you're on Firefox, make sure to right-click and select "Save Link As…" because if you just click normally on the link it will try to install it as a Firefox extension.)
  4. Open the Add-ons page in Thunderbird.
  5. Either drag and drop the downloaded XPI file onto the Add-ons page, or click the gear icon and select "Install Add-on From File…".
  6. Once you've clicked through the install dialogs, you can delete the downloaded XPI file, since Thunderbird makes a copy of it during installation.

To switch back to the main (non-beta) release channel at any time, repeat the above steps but download and install "send_later.xpi" instead of "send_later_beta.xpi", or download and install the current version from addons.thunderbird.net.

You can report issues with beta releases as GitHub issues or via email, or discuss them in our discussions forum or on our mailing list.

New features

You can now store scheduled drafts in a subfolder of your main drafts folder! This can be configured in the Send Later options. Note that this does not work for Gmail accounts, unless you configure Thunderbird to store drafts in a folder other than the default "[Gmail]/Drafts".

Return receipts work now. Delivery status notifications still don't work, because it's impossible to make them work due to limitations in Thunderbird, but Send Later no longer allows you to schedule a message that has delivery status notifications enabled on it.

You can now "claim" one or more messages that were scheduled in another Thunderbird instance by selecting them and then using the appropriate Send Later command in the message context menu. They are moved over to being managed by the Thunderbird profile in which you do the claiming, and their schedules are otherwise unmodified.

You can now disable one or more of the shortcuts and remove them from the scheduling pop-up by selecting "(none)" for their function names in the preferences.

If you use "Send delays messages" or "Send does Send Later", you can now designate a particular address book by name as a whitelist of recipients whose messages don't need to be scheduled. If all of a message's recipients are in the address book, then when you click the Send button or select the Send menu command, Send Later is skipped.

You can now change the key bindings for the shortcut keys (Ctrl-Alt-1, -2, -3) use other keys if you don't like 1, 2, and 3 or if they conflict with other extensions.

Improvements

If you click the Send Now or Put in Outbox button after changing something in the pop-up, you now get a confirmation pop-up to make sure that's what you meant to do. You can disable it if you don't like it.

If you hit Enter in the pop-up while you're focused on one of the buttons, that button is activated, as opposed to the previous behavior where Enter always activated the "Send at" button even if you were focused on another button.

In previous releases of Send Later, allowing multiple instances of Thunderbird to operate on the same messages could be problematic, because if Thunderbird's internal identity keys differed between the two instances then messages scheduled on one instance and delivered on another could end up being sent through the wrong email account. Send Later now makes a best effort to avoid this by finding the appropriate identity for a message at delivery time and telling Thunderbird to use it.

The scheduling window is resized if it's too short to fit the content without scrolling, unless it would need to be resized by too much.

There is a new advanced preference called compactDrafts which, when enabled, tells Send Later that at the end of each scheduling run it should compact any Drafts folders from which messages were deleted. If you use Send Later with a Gmail account and are annoyed by the fact that messages delivered by Send Later don't get removed from your Drafts folder in the Gmail app, this will fix that.

Bug fixes

The date/time pickers in the scheduling popup couldn't be used in some locales because when they were used the date that got inserted into the text field as a result was unparseable by Send Later. Now when all other attempts to determine a parseable date format fail, Send Later uses JavaScript's built in "ISO" date format, which is guaranteed to be parseable by Send Later regardless of locale.

The confirmation message that Thunderbird is supposed to pop up when you type Ctrl-Enter and you're not using Send Later for it has been fixed.

Send Later was previously putting the scheduled send time in the Date header of messages (when that feature was enabled in the preferences) only when initially scheduling messages, and not when rescheduling recurring messages. Now it does the right thing in both cases.

For some reason the "Are you sure? Yes / No" confirmation messages in the options tab were not localized, i.e., they were always in English even when the rest of the add-on was in a different language. This has been fixed.

The Autocrypt header has been restored to outbound emails for users who have it turned on in their account settings.

We've fixed a bug which could potentially spam the error console with errors every minute for an extended period of time when there is a pending message which can't be sent because of day-of-week restrictions.

Release 10.1.x

This is an exciting release with many new features and improvements!

New features

Collection of anonymous usage data

We're putting this first in the release notes because we think it's important to be fully transparent about things like this: starting with this release, Send Later collects anonymous usage data to help us improve the add-on, measure its usage, and identify where to focus our efforts.

We're extremely careful to ensure that there's nothing private or personally identifiable in the data we collect and certainly no information whatsoever about your email or email accounts. We don't even capture your IP address on the server to which the collected data is sent. It's a private server under our exclusive control, and we don't share the data with anyone.

When the add-on is installed or upgraded to the new release you will be asked whether you wish to participate in data collection, but note that it is enabled by default since there is no personally identifiable or private information in the collected data. If you just close the prompt window rather than responding, the add-on will keep asking each time you launch Thunderbird until you answer.

See our privacy policy for additional details, including details about the data we collect and how to change your mind and opt in or out when you've already responded to the pop-up.

Bulk scheduling messages from the message list

You can now select one or more drafts from the message list, right-click or ctrl-click to bring up the menu, and elect "Send Later > Schedule message(s)" to bring up scheduling window and schedule all of these messages at once. When you specify the desired schedule and click the "Send at" button, Send Later opens the selected messages one by one and schedules them as requested.

If one of the selected drafts was previously scheduled, the old schedule is overwritten. If it was previously scheduled in a different Thunderbird profile, it is switched over to being associated with profile in which you just rescheduled it.

Note that you can also use the "Send Now" or "Put in Outbox" button here, which means you can use this to send a bunch of drafts or put them all in your Outbox all at once, rather than editing them one by one to do it.

There are two important caveats for users of end-to-end encryption, due to gaps in the Thunderbird add-on APIs (this information is for Send Later 10.1.2 and newer):

  1. This does not work for messages in accounts or identities which have PGP encryption or signing enabled by default, even if you previously disabled encryption and signing when saving the draft.
  2. Drafts scheduled like this are sent with your default S/MIME encryption and signing settings regardless of what S/MIME settings the draft was previously saved with.

Skipping the next occurrence of recurring messages

You can now select one or more scheduled messages in your drafts folder, right-click or ctrl-click to bring up the menu, and select "Send Later > Skip next occurrence" to skip the next occurrence of the selected message(s). For example, if you have a message next scheduled to be sent today at 10:00, and at 9:30 you skip its next occurrence, it is rescheduled to tomorrow at 10:00.

This fails (and logs the failure in the error console, though there is currently no pop-up notification) in these circumstances:

Improvements

Since we had to remove support for the Send Later column in the message list in drafts folder in Thunderbird 115 (we're hoping to bring it back once Thunderbird's add-on APIs support it), it has become harder to find scheduled messages and see when they are scheduled for. To mitigate this, Send Later now puts the send time in the "Date" field, so it's visible in the "Date" column of the message list. If you've got messages in a drafts folder with dates in the future, they're probably scheduled messages! If you don't like this behavior, you can turn it off by setting the "scheduledDateField' preference to "false" in the advanced configuration editor.

Send Later no longer forces the toolbar button to be visible in compose windows by default in Thunderbird 115. Although it is visible by default when Send Later is installed, you can now customize the toolbar and remove it if you wish. In the absence of the toolbar button, you can still activate Send Later by typing ctrl-shift-enter (ctrl-shift-Command on macOS), or using the "File > Send Later" menu command, or by clicking the Send button if you have the "Send does Send Later" preference enabled, etc. The only thing you can't do without the toolbar button is activate the shift-click and control-click shortcuts (if any) configured in Send Later's preferences. This improvement is not possible for Thunderbird 102, so Send Later is still forcing the button to be in the toolbar for Thunderbird 102 users.

Send Later now displays the release notes automatically when it is installed or upgraded to a new major or minor release. This can be disabled by setting the releaseNotesShow preference to false in the advanced configuration editor. Also, the release notes page has been changed from the GitHub releases to the page you're reading right now, and instead of opening it in a browser it is now opened in a Thunderbird tab.

You can now zoom in and out (i.e., make everything bigger or smaller) in the scheduling pop-up by typing Ctrl-Plus or Ctrl-Minus or Command-Plus or Command-Minus. As of 10.1.2, the zoom level, and also the window dimensions if the pop-up isn't attached to the message window (i.e., the toolbar button isn't visible in the compose window), are preserved between invocations.

A bunch of tooltips, mostly in the preferences window but some in the scheduling pop-up, that were lost in the conversion of the add-on to Thunderbird 78 have been restored. That is, there are now some useful detailed explanatory messages that display when you hover the mouse over certain settings and buttons.

Send Later now prevents messages with schedule dates more than six months in the past from being delivered automatically, even if you have the preference for enforcing that disabled or set to a value higher than six months. This is necessary because Send Later keeps records of all delivered messages to prevent it from accidentally re-delivering a message if something goes wrong, and we don't want to have to keep those records around forever taking up increasing disk space and having an increasing impact on performance. Now that we're enforcing a six-month maximum delay for message delivery, Send Later can safely remove any delivery records older than six months, so that's what it now does.

Previously, if you opened Send Later's preferences, made changes in the advanced configuration editor at the bottom but did not save them, made different changes in the top section of the preferences page, and then saved the advanced configuration editor, the changes you'd made in the top section of the page would be overridden. Now when you make changes at the top, they're automatically copied into the advanced configuration editor so they won't be overwritten if you then save its contents.

Speaking of the advanced configuration editor, the settings there are now sorted alphabetically to make it easier to find the ones you're looking for.

Send Later no longer saves bad or incomplete custom date formats in your preferences. Instead it warns you that the format is invalid and won't save it until you fix it.

The hidden "checkTimePref_isMilliseconds" preference is gone. The frequency with which Send Later checks for messages to be delivered can no longer be set in milliseconds. If you were using this preference then Send Later should convert it automatically on upgrade, but you might want to check your preferences to make sure.

A misleading Italian translation of the "Trigger unsent message delivery from Outbox" setting in the preferences window has been updated to make it clearer. This plus the tooltip will hopefully make it much less likely that someone will uncheck this preference when they shouldn't.

The capitalization of the name of the add-on in German has been fixed; it should be "Später senden", not "Später Senden" (not the change in capitalization).

Many other updates have been made to Send Later's translations. Thank you, as always, to our many dedicated translators who make Send Later accessible to users all over the world!

Bug fixes

When some users edited and went to reschedule a scheduled message, the previously scheduled date that Send Later put into the text field in the scheduling pop-up had the month and day reversed. This is now fixed for users for whom it can be fixed automatically. If you're still seeing this issue, see the user guide for how to address it.

For users of Send Later in English on macOS, the access key for the "Send Now" button in the scheduling pop-up wasn't working, i.e., you couldn't type Ctrl-Option-N to activate the "Send Now" button. This is due to either a macOS bug, or a Thunderbird bug, it's not clear which, but in any case, we've implemented a workaround in Send Later, so the access key works now.

Previously, if you had end-to-end encryption or signing enabled on a message and then scheduled it it with Send Later, it would be sent without encryption or sending. Although it is not yet possible to send encrypted or signed messages with Send Later, now when you try to schedule a message when encryption or signing is enabled, Send Later warns you about this and prevents you from scheduling the message.

Thunderbird added a new internal "Autocrypt" header to drafts when end-to-end encryption is enabled for an account. Send Later didn't know about this header and therefore wasn't stripping it out before sending scheduled drafts. Now it does.

To minimize confusion the "Show Send later column" preference is hidden in the preferences tab in Thunderbird 115 since the column is not currently supported.

The title bars of some pop-up windows opened by Send Later now have a separator between the title and the words "Mozilla Thunderbird", rather than those being glommed right onto the end of Send Later's specified title with no space separating them.

We believe some users may have been getting error pop-ups about their Drafts folders being corrupted when that wasn't actually the problem. We've fixed at least some cases of this, though we don't know if we got all of them.

There were some contexts in which the log level was not being set properly so more was being logged than should have been. We believe this has been fixed.

Known issues

Please check the user guide for persistent caveats and known issues. See also our GitHub issues page for new issues that may not have been triaged or made it into the user guide yet, or for which a fix is pending.

Under the hood

Users are unlikely to notice this, but it is worth mentioning that the code for migrating preferences from the legacy add-on preferences system into modern preferences storage has been removed. This can only impact you if you've been using Send Later on a version of Thunderbird so old that it doesn't support modern preferences storage and then you upgrade, in which case you'll have to reconfigure any non-default Send Later preferences. Versions of Thunderbird without modern preferences support have been obsolete, unsupported, and not receiving security updates for several years, so it was time for this old code to say good-bye.

The "experiment" code for saving messages into the user's Drafts folder when scheduling the next instance of a recurring message, and for copying messages into the user's Outbox during delivery, have been replaced with code that uses the supported Thunderbird add-on APIs. Send Later is still using quite a bit of experiment code (as noted elsewhere, this is why when you install it Thunderbird warns that it has full access to your computer), but we are gradually getting rid of it as the add-on APIs are enhanced to support more of what Send Later needs to do.

Release 10.0.x

New features

Thunderbird 115 support!

Improvements

The Send Later button is the main Thunderbird window is no longer disabled when the sendDrafts preference is false, so you can access the pop-up with the list of scheduled messages preferences link, etc.

The warning about quitting Thunderbird when scheduled messages are pending no longer displays when the sendDrafts preference is default, since in that case the Thunderbird instance that the user is quitting is not actually responsible for sending those scheduled drafts.

The explanatory strings inserted into the text fields of the function editor when the user goes to create a new function are now inserted as placeholder strings, rather than as actual text that the user needs to delete.

Bug fixes

Scheduled message delivery is now reliable while the Thunderbird window is minimized in Thunderbird 115. Prior to this fix, messages sometimes were not delivered in a timely fashion when the window was minimized due to internal Thunderbird changes.

Scheduled message delivery is now reliable for users of Owl for Exchange, thanks to a workaround introduced to address a mysterious internal issue with Thunderbird or Owl (it's not clear which).

The ctrl-alt-1, -2, and -3 shortcuts in the message compose window work again.

The ctrl-click and shift-click actions on the Send Later button in the compose window works again.

Send Later key bindings now work properly even when the user has remapped the relevant keys on their keyboard.

Send Later now treats the Enter key on the numeric keypad the same as the one on the users main keyboard.

Send Later is now more reliable about warning the user when they quit Thunderbird while scheduled messages are pending.

Send Later no longer puts duplicate copies of scheduling function names in the pop-up menus on the preferences page when the user edits and saves an existing function.

The user guide link on the preferences page was wrong and is now fixed.

Send Later no longer calls the user's scheduling function repeatedly when the scheduling pop-up opens. This makes Thunderbird more responsive and eliminates multiple unnecessary calls to any web APIs invoked from the scheduling function.

Known issues

Under the hood

The contributed library of dynamic scheduling functions has been cleaned up and made compatible with the current version of Send later.