Gnus and Maildirs
For the most part, maildirs are just another backed in Gnus, but there are some idiosyncrasies with respect to expiry mechanisms that bear mentioning.
1. Although nnmail-expiry-wait is honoured, it seems that neither nnmail-expiry-target nor expiry-target are honoured. Instead, you have to set expire-group in group parameters. expire-group seems to be entirely maildir specific. This little gem is buried away in the Gnus manual, but I managed to dig it out. It's in section 184.108.40.206, under the section describing expire-group. There's a line that goes like this:
Even if this parameter is not set, nnmaildir does not fall back to the expiry-target group parameter or the nnmail-expiry-target variable.
Why is it like this? I have no idea. It seems stupid.
So, anyway, my setup looks like this:
(setq nnmail-expiry-wait 30) (setq gnus-parameters '(("INBOX" (expire-group . "Archive-INBOX")) ("folder01" (expire-group . "Archive-folder01")) ) )
Please note that if the groups are from a primary select method, you must not use the long form of the group name (i.e. specifying the backend, etc.)
I haven't figured out a way to make this automatic, in the way that expire-target can take a function to compute the group name. You can set a function instead of a string, but I think it's called for every article, which is not quite what I want.
2. Apparently, Gnus handles flags in a non-standard way. This harms interoperability.