Open your Pine Email account
Open the desired Folder to export messages from
Press semicolon ;  for the select command
You may Press A to select All
or Press N for the "select by number" command
If selecting by number enter the message numbers (found on the left of the screen) separated by commas or a range of numbers separated by a hypen. 1,3-90 selects messages 1 and messages 3 through 90.
Press A for the "apply command"
Press E to Export
Enter a file name, preferably ending in  ".txt"
Press Enter to save the messages to the file
FTP the file from the email folder to your local computer.
Open the file on the local computer and check its contents before deleting the messages
Go back to the telnet window and press A for Apply and D for Delete
Delete the FTP'd file from the email account using FTP. Be sure you are deleting the email account file and not the local file.

If you are very short of space in your email account, you may have to export and delete a smaller number of messages to begin with in order to make room to export a larger batch.