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

Thunderbird, Postbox

Previous Message

Get Real Previous Message

Get the previous message. Unlink the default Thunderbird buttons this just go to the previous in the list, or if shift is pressed, the previous unread.

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

Remote Content

Set the exceptions for what remote content can load.

Opens the window to set exceptions for the loading of remote content

Compatibility: Thunderbird, Postbox SeaMonkey

Return Receipt

Toggle Return Receipt on/off

Toggle the sending of a return receipt on and off.

Compatibility: Thunderbird, Postbox SeaMonkey

Rewrap

Rewrap

Rewraps the message text

Compatibility: Thunderbird, Postbox SeaMonkey

Save Attachments

Save All Attachments From Message

Save Attachments from an message.

Compatibility: Thunderbird, Postbox SeaMonkey

Search Addresses

Open Addresses Search

Open the advanced address search window.

Compatibility: Thunderbird, Postbox SeaMonkey

Search Messages

Open Message Search

Open the advanced message search window to find an email.

Compatibility: Thunderbird, Postbox SeaMonkey

Send & Receive

Send and receive messages

Send all messages in the outbox and get all new messages.

Compatibility: Thunderbird, Postbox SeaMonkey

Send Without Save

Send message without saving a copy

Send message with out saving a copy to the sent folder. If you want this as the permanent behaviour, there is an option in account settings under 'Copies & Folders'

Compatibility: Thunderbird, Postbox SeaMonkey