Separate out video linkifying from normal url linkifying - separate settings
Add Message-ID header value to custom field (postie_message_id?) to both posts and comments.
Use In-Reply-To header value as a better way to detect replies
Verify that {TITLE} is doing the right thing.
Automatic updates for AddOns: 
    https://github.com/seedprod/sellwp-updater
    http://code.tutsplus.com/series/create-a-license-controlled-theme-and-plugin-update-system--cms-760
automatically create category if it doesn't exist. new option to allow this feature?
Add setting for category detection. I.e. checkboxes for [], -- and : styles. Default to all on.
Add setting to not remove category text from subject/title
Comment not being created when subject contains category command []. I.e. listserv subject lines
date: tag is being detected in body when not wanted
Update tag_* and filter_* to handle HTML (per tag_Tags)
dynamically determine video size (height/width) - https://code.google.com/p/phpvideotoolkit/
gallery logic does not handle both images and non-images
plugin conflict - Image Rotation Fixer/Image Rotation Repair
send email notice when attachments are rejected.
readme tips http://wp.smashingmagazine.com/2011/11/23/improve-wordpress-plugins-readme-txt/
review http://codex.wordpress.org/Settings_API
use wordpress plugin template
  boilerplate http://wppb.io/
  starter-plugin https://github.com/mattyza/starter-plugin
  WordPress-Plugin-Template https://github.com/hlashbrooke/WordPress-Plugin-Template
configurable message for "post confirmation" - variable substitution
add hooks for post meta data change
  post type
  post format
  category
  date
  comment control
  excerpt
  tags
  author
add hooks for content changes
  attachment template
  subject/title
  post begin
  post end
  signature strip
hook for actions
  post failure
  post success
  media attachment
  non-permitted attachment types
  email rejected
  email connection failure
  start check
  end check
  mail read
  mail delete
  content part
collect and send last debug log and system info (see http://wordpress.org/plugins/send-system-info/)
Support EXIF orientation via PHP Exif Library https://github.com/lsolesen/pel

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Revised parsing logic

convert all logic to filters
before session filter
before mail filter
email/account filter
attachment filter
iterate through each html element (p, div, etc) and apply all filters and buffer output
after mail filter
after session filter

convert plain text to html using same logic as wp - i.e. all text is html
Original text is never modified
There are filters that modify
  meta data (tags, categories, date)
  content (start, end, newlines, linkifying)
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AddOn Ideas
(done) Google Alerts - turn each alert into a post
(done) HTML cleaning - use http://htmlpurifier.org/ to convert Word Html and other bad html into standard html

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Postie 2.0

http://www.yaconiello.com/blog/how-to-write-wordpress-plugin/

setting to turn off individual tags
process single email at a time and don't delete unless successful
plugin mechanism to add new tags (and define "built-in ones")
fix postie settings	http://alisothegeek.com/2011/01/wordpress-settings-api-tutorial-1/
Make sure all failures are sent to admin (option?) failed attachments, etc.
Option to send logs to support
Enhance #img# to specify the featured image
"yoast" style admin sidebar - see clicky by yoast
replace native imap MIME parser with flourish - http://flourishlib.com/docs/fMailbox or Hoard - see "Post By Email" plugin https://wordpress.org/plugins/post-by-email/
provide a location for custom icons. update docs about location.
handle condition where only one of text/plain & text/html is supplied, but Preferred Text Type is set to the opposite.
change all Postie command to use a more consistent and easy to parse syntax
  Use standard shortcode syntax. I.e. [postie date="Jan 1, 2014"]