Can't get expiry to work

[David Sumbler]

I use procmail to sort incoming mail into various folders, but I also
keep a copy of every incoming mail in a folder called "Backup" - just
in case.  When I used to use Pine, I would usually keep stuff in there
for about a month, then delete it.

Now that I use Gnus, I have put 

((total-expire . t)
 (expiry-wait . 31))

in the group parameters for "Backup".  I have also tried pressing "E"
against various mails in the summary buffer.  But even when I do C-c
C-x in the group buffer, no mails actually get deleted.  However, when
leaving the summary buffer, or when doing the C-c C-x, I get messages
indicating that Gnus is expiring and deleting things.  But it isn't.

Have I misunderstood something?  I expected any mails with a date more
than a month ago, and certainly any that I specifically marked with an
"E", to be deleted.  Or does it work from the date they arrived in the
folder, which I only created a few days ago?

Incidentally, is there a way of getting Gnus to mark all incoming
mails to this folder as read?

David

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