AttachmentCount for Thunderbird
Adds a column to the Thunderbird message list to always display the true attachment count. An icon is shown for single attachments or all attachments deleted/detached. Tooltip preview of single attachment content and summary for multiple attachments.
Thunderbird 60 - AttachmentCount v4.1
Thunderbird 68 - AttachmentCount v5.8
Thunderbird 78 - AttachmentCount v6.4
The thread pane (message list) columnpicker is used to select the Attachment Counts column; it may then be dragged to whatever position you like.
If there is only 1 attachment, an icon will be shown for its content type. If there is no content type, it is derived from the file's extension (it is possible to spoof a different content type from the document's real type).
If all attachments are deleted or detached, an appropriate icon will shown.
Check the "Show count" setting in Options/Preferences in Add-ons Manager to show the number rather than an icon.
Sorting by the Attachment Counts column results in a number ordered and content type ordered list. Grouped by Sort is also supported and buckets for counts and types are shown in that view.
The status icon of an attachment is updated automatically on an attachment detach/delete. A shift-click twice on the column header may be performed to refresh the counts/status - for messages in the visible rows only. Click on the column row to refresh an individual message's counts or when updating Preview content types.
IMAP: In order for IMAP message attachment counts to be calculated, the message must be downloaded if it is unavailable locally. The default is to download and calculate, and as this is asynchronous there should be little delay effect even for large attachments. If this is undesired, uncheck the "Download imap" setting in Options/Preferences in Add-ons Manager. Instead of counts, the generic attachment icon will be shown instead.
NNTP: The api used to get attachment counts is not available for newsgroup (NNTP) attachments, so counts aren't available.
Preview: A simple preview has been implemented for single attachments in the thread pane, without the need to select the message. Hover the icon to show a preview of approximately the first page in a tooltip. The active icon is highlighted.
Preview is enabled (default) by checking the "Enable Preview" setting in Options/Preferences in Add-ons Manager. Any content type may be previewed, but only text types are readable. A number of rules have been pre-added. Users may add additional content types. The list of officially registered types is here.
For messages with multiple attachments or non previewable attachments, the tooltip consists of a summary display with filename, contentType, and detached file path or remote url for each attachment.
Comments, Questions, and Bugs: