To mark and delete all messages in Pine, do:
How do I mark all messages in a newsgroup as "read" or "deleted"?
First, you need to make sure that you have access to all the commands necessary.
From the [M]AIN MENU, choose [S]etup and then [C]onfig, then make sure that there are 'X' marks next to these two options:
To mark all messages as "read" or "deleted" press and release each of the following:
; = Select
a = All
a = Apply
* = Flag
which will bring you to the FLAG MAINTENANCE screen (if you do not have enable-flag-screen-implicitly set in SETUP CONFIGURATION, select "^T To Flag Details" to reach it now):
Set desired flags for current message below. An 'X' means set it, and a ' ' means to unset it. Choose "E Exit Flags" when finished.