empty trash

[questioner]

how can I empty all at once, not individual items?

 

[Bruce Hagen]

Trash as in Deleted Items? Right click on the folder and Empty Deleted
Items.

If you're speaking of other folders:

To delete all: Highlight one and Ctrl + A will highlight them all. -
Delete.

To delete a section: Highlight the first one you want to delete. Scroll
down to the last one and click on it while holding the Shift key down. -
Delete.

To delete multiple messages that are interspersed: Hold down the Ctrl key
while you click on each message to highlight. - Delete.

Also: Shift + Delete will bypass Deleted Items.