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

Thunderbird, Postbox

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

HTML Mode

Set if Message is shown as HTML or Plain Text

Set if the message is displayed as HTML, sanitized HTML (all the possible nasties removed) or as plain text.

Compatibility: Thunderbird, Postbox SeaMonkey

Open in Conversation

Open current message in Conversation

Open the current message in a conversation tab

Compatibility: Thunderbird, Postbox SeaMonkey

Purge

Compact Folder, and Delete Junk

Delete all junk emails then compact all folders. Quick way to do both at the same time.

Compatibility: Thunderbird, Postbox SeaMonkey

Skip Trash

Delete message with out sending it to the Trash

Delete a message with out sending it to the Trash. This will completely remove the message so that it can not be recovered.

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