Beta version 8.0.15 (release candidate 2)

This version fixes lots of various minor bugs, and adds some safety precautions for handling edge cases including corrupted Outbox and/or Drafts folders.

Features:

• On fresh install or version upgrade:
  • Suggest (but not require) that users restart Thunderbird when a new Send Later version is installed. In my personal experience this seems to fix many of the reported issues. This will hopefully not be necessary in future updates, but it seems to help in cases where a prior beta release failed to unload itself completely.
  • Compact the Outbox and Drafts folder(s). If there are any messages in the Outbox, or any scheduled messages in the Drafts folders alert the user about them and prompt for option to disable Send Later until potential issues are fixed. A "soft" disable in this case means that the check interval is set to 0, which prevents Send Later from executing its main loop code, effectively disabling its sending functionality. The user will have to manually change that option back in preferences in order to reactivate full functionality.
• Re-introduce the header display when viewing scheduled drafts. This is in addition to the Send Later column and the toolbar popup in the message view panel.
• The "advanced configuration editor" is slightly more usable, and offers visual confirmation when options are successfully changed / alerts if input cannot be parsed.

Bug fixes:

• The logic around sending messages is now almost verbatim taken from the legacy code, which will hopefully clear up some sending-related issues.
• Reworked the Drafts folder column overlay, which will hopefully improve its reliability. Note that sorting by schedule doesn't always work.
• Be more careful about cleaning up all overlay components when the addon is removed or upgraded.
• Fix UI formatting of schedules with cancel-on-reply and/or function arguments.