There is a column in Thunderbird that indicates that a message has an attachment, and I believe it's visible by default, though I don't know where it falls in the default column order as I've shifted columns around so many times for testing that I do not remember the original order.  The Mozilla Apps Enhancements add-on includes commands specifically dedicated to making it easy to rearrange columns and/or show and hide columns in Thunderbird.

The following is a brief tutorial I wrote as part of the "cheat sheets" I make for my tutoring clients when they're getting started with a screen reader and are using Thunderbird.  The first bit about the Quick Folder Key Navigation extension is something that anyone using a screen reader with Thunderbird needs to do as soon as they possibly can, if they haven't done it already.
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Thunderbird e-mail client

IMPORTANT:  For those using Thunderbird with a screen reader I strongly suggest installing the Quick Folder Key Navigation extension.  This allows you to jump from folder in the folder tree using first letter navigation to move between them.  Without it, this does not always work.   You will only need to install this extension once for any instance of Thunderbird you might be using.  If you are using JAWS or NVDA, searching for this add on within Thunderbird is quite simple:

·         Activate the Tools Menu (ALT+T), add-ons option (followed by A) and tab 3 times, at which point you should be on the Extensions Pane.  If you happen to land on any other pane then use Down Arrow (or Up Arrow) until you hear Extensions.

·         Tab 2 times, which lands you in the search all add-ons edit box. 

·         Then type in Quick Folder Key Navigation, hit enter, and wait a few seconds for the search to complete. 

·         Tab 5 times more to gain focus on the list of results.  Then hit Down Arrow to start navigating the list.  Quick Folder Key Navigation should be the first result.

·         Tab 2 times to land on the Install button then hit enter.

·         After the install completes you need to exit Thunderbird and start it up again for this extension to become active

 

Upon opening Thunderbird, you will be in the folder tree sitting on whatever folder you had open the last time you closed it.  You will still have to hit TAB until you reach the folder tree view.

When in the folder tree view you can use first letter navigation to move around (if you installed the extension noted above).

When you are sitting on a folder in the folder tree view hitting TAB will take you to the message list.  You know you’ve arrived when you hear, “List View.”  Use up and/or down arrow to navigate through the list of messages.  [Depending on the screen reader you usually have to hit TAB either once or twice.]

If you are using threaded view, and hear JAWS announce “Level zero, collapsed,” use the right arrow to expand the thread to show all its individual messages.  To collapse the thread, get back to the first message at level zero and hit the left arrow.

When you land on the message you want to read, hit Enter to open it in a dedicated reading tab.

You will use the usual reading commands to read through the message that you use in any other program.

Thunderbird Shortcuts

Hit CTRL+W to close a reading tab and go back to the message list for the folder you had been viewing.

Hit SHIFT+TAB (once or twice) or F6 to move back to the folder tree from the message list for any folder.  This must be done after you delete all messages in a given folder as well.

To select messages in the message list view:

            Once you are in the message list view, and have a specific single message selected:

1.      Holding SHIFT, while at the same time hitting either Up or Down Arrow will continue selecting messages in the direction you are moving.

2.      Holding SHIFT, then hitting PgUp or PgDown will select all messages above or below the currently selected message, respectively, stopping with the first/last one currently displayed in the message list view.

You can use CTRL+A to select all messages, including ones currently not visible in the message list view.  Unless you’re certain about doing whatever you intend to do with ALL messages, use this option with great caution.

To delete messages:

1.      If you are in the message list view, select the message or messages you wish to delete then hit the Delete key.  This will move them to the Trash folder and none will be opened for reading if you use this technique.

2.      If you are reading a message and want to delete it, hit the Delete key and it will delete that message and automatically open the next message in the folder for reading.

To reply to a message you’re reading:  CTRL+R opens the Write window with the subject filled in with “Re:” prefixing it and the text of the message you’re replying to quoted.  Your cursor will be sitting right after the quoted material waiting for you to type.  If  you’re trying to do a Reply All that’s CTRL+Shift+R

To create a new message, regardless of what you’re doing in Thunderbird, hit CTRL+N.  This opens the Write window waiting for you to fill in your addressees in the “To:” edit box.  As you hit Enter after filling in an address or choosing one from the dropdown list of previous addresses another edit box of the same type opens.  If you need to change from “To:” to “CC:” or “BCC:” then hit SHIFT+TAB, use the up/down arrow key to find what you want, then hit TAB again to go to the edit box for the address.

·         To add attachments to an outgoing message, hit CTRL+SHIFT+A to bring up the Attach Files dialog.  It is very similar to a Save dialog except it works “in reverse.”  You will need to navigate to the location of the file you want to attach, select it, then either tab to the Open button or hit ALT+O to attach the file to the message.

To send a message, whether it’s a reply or a new message, hit CTRL+ENTER when you’ve finished composing.  It will send immediately and close the Write window, taking you back to wherever you had been before hitting the reply or new keyboard shortcut.

To get to attachments on an incoming message hit ALT+M, H  [Opens the Message Menu and selects the Attachments option]

 

Creating Folders in Thunderbird

            You can create folders within Thunderbird to organize your e-mail.  The concept is the same as in Windows File Explorer, and the tree view will be the starting point.

1.      In the tree view navigate to the folder or account (if you want the folder directly under the account like Inbox, Sent, etc., typically are) under which you want your new folder nested.  In most cases this will be your e-mail account itself, unless you are creating subfolders within other existing folders.

2.      Hit ALT+F,N,F – File Menu, New Option, Folder Option – after which the New Folder dialog opens and you’ll be in the edit box in which you’ll type the new folder’s name.

3.      Tab to the Create Folder button then hit enter, or hit ALT+R.  Your new folder has been created.

 

Moving Messages Between Folders on Thunderbird

1.      Select the message or messages you wish to move.

2.      Bring up the context menu with the applications/menu key or Shift+F10, then hit M [Move]

3.      You will be presented with a submenu that will vary somewhat depending on your folder structure, you have to drill down through the submenu to locate the folder where you want the selected messages to be moved.

4.      Once you have focus on that folder, hit Enter and the message(s) will be moved there.

 

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Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363  

Science has become just another voice in the room; it has lost its platform.  Now, you simply declare your own truth.

      ~ Dr. Paul A. Offit, in New York Times article, How Anti-Vaccine Sentiment Took Hold in the United States, September 23, 2019