Using cache to read IMAP mail offline, with proper deletion of Spam

[ding_gnus.org@sumou.com]

Hello:

I've been searching and experimenting very hard, however not with 100%
results, perhaps someone can help me.

What I want to do:

1. Use Gnus to access my mail via IMAP.
2. Store every read message in the cache, so that when I'm offline I can
reread it.
3. Purge all deleted messages properly.

It's the third part that I cannot get to work properly, requiring
cumbersome deletion.

I have the following .emacs settings, relevant to the above points:

(setq gnus-select-method '(nnimap "SERVER.ADDRESS"
				  (nnimap-address "SERVER.ADDRESS")
				  )
      )
(setq gnus-use-cache t)
(setq gnus-cache-enter-articles '(read ticked dormant))
(setq gnus-cache-remove-articles '(unread))

The above sets the cache, so that emails that I read when online get
downloaded and don't have to be redownloaded the next time I access
mail, allowing for offline reading when not online.

The ones that are for instance read, and seen as spam, are then marked
unread, and should exit the cache because of the last line above.

What this results in.

To delete files also from the server, so that they are not kept
in the cache and stick around forever, I have to follow the
following steps:
1. Read the emails.
2. Mark them as expirable with `E'.
3. Delete all expired items with `B M-C-E'.
4. Exit the Summary Buffer to the Group Buffer with `q'.
5. Enter the mailbox again.
6. Display all the mails with `/ o' to display also the read
    emails, this will display also the expired/deleted items,
    which have still been kept in the cache.
7. Read each of the emails and mark it unread with `M-u'.
8. Exit the Summary Buffer to the Group Buffer with `q' again.
9. Update the Group Buffer with `g'.
This then, and only this, deletes the expired/deleted emails and remove them
from the local cache. The items will be deleted from the IMAP
server and locally, thus disappear everywhere.

It's an uncomfortable hack, but I've found no better way so
far to be able to utilize the cache, so big mails don't have
to be redownloaded upon every reconnect.

How I can I set it, so that when mails are marked as expirable with `E'
and then expundeg with `B M-C-E' they don't stick around and have to be
opened and un-read, but are deleted? Does anyone know?

Thank you.

ShiroiKuma