These are a ready make selection of some of the most popular buttons from the Custom Toolbar Button Maker

Thunderbird, Postbox

Threads with Unread

View Threads With Unread

View only the threads in the current folder that have unread messages.

Compatibility: Thunderbird, Postbox SeaMonkey

Unread Threads

View Unread Threads

View threads that you have not read yet.

Compatibility: Thunderbird, Postbox SeaMonkey

Watched Threads with Unread

View Watched Threads With Unread

View watched threads that have unread messages in them.

Compatibility: Thunderbird, Postbox SeaMonkey

All Threads

View All Threads

View all the threads in the current folder, not just unread or some other sub set.

Compatibility: Thunderbird, Postbox SeaMonkey

Download/Sync Now…

Run download and sync before going offline

Runs the download and sync now tool, so that messages can be used when you go offline.

Compatibility: Thunderbird, Postbox SeaMonkey

Edit as New

Edit Message as New

Edit an email.

Compatibility: Thunderbird, Postbox SeaMonkey

Get Inbox

Change Focused Folder to the Inbox

Change the currently selected folder to your Inbox.

Compatibility: Thunderbird, Postbox SeaMonkey

Insert

Show Insert Menu

Show Insert Menu

Compatibility: Thunderbird, Postbox SeaMonkey

Message

Show the Message Menu

Show the Message Menu

Compatibility: Thunderbird, Postbox SeaMonkey

Paste As Quotation

Paste as a Quotation

Paste text so that it appears as a quoted message.

Compatibility: Thunderbird, Postbox SeaMonkey