Re: mail split with multiple backends

[Didier Verna <didier@lrde.epita.fr>]

Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) wrote:

> There are a number of ways to do it.  One possibility is this: suppose
> you have nnml and nnfolder backends.  Then you set up
> nnmail-split-methods for nnml and include a rule which puts all
> nnfolder messages into a special group; nnml:nnfolder, say.
> 
> Then you enter that group, `M P a' to process-mark all articles,
> temporarily change nnmail-split-methods to a value which is good for
> nnfolder, then `B r' to resplit the messages using the new
> nnmail-split-methods.  Specify nnfolder as the backend to use.
> 
> The second alternative is to have some program outside of Gnus which
> splits the mail (such as procmail).  Then you set mail-sources such
> that it only picks up the nnml part, get new mail, then set
> mail-sources such that it only picks up the nnfolder part, and get new
> mail again.  You also have to arrange that the first time you get new
> mail, the nnml backend gets it, and the second time you do it, the
> nnfolder backend gets it.

        There's a thrid possibility that I use in a backend I wrote (I'll tell
you what it is soon on this list, as it might be of some interest): the idea
is that you tell *both* backends to retreive mail, but in one of them, you
override the mail-source and split-methods variable.

        So you can do this for instance:
- As in Kai's second option, you split your mails in two different "source"
  files (with procmail for instance)
- You set *both* <backend>-get-new-mail variables to t
- You define the variables nnml-mail-sources and nnml-split-methods (if you
  decide that nnml is the secondary backend
- And finally, you rewrite the nnml functions that get mails, in order to wrap
  their code in a 'let statement that will allow you to temporarily assign
  different values to mail-sources and split-methods.

        For instance, all calls to nnmail-get-new-mail should be wrapped in
something like:

  (let ((mail-sources nnml-mail-sources)
	(nnml-split-methods nnml-split-methods))
    (nnml-get-new-mail 'nnml nil nnml-directory group)))


This method is very nice because all you have to do is type 'g' in order to
get mails from/for multiple mail backends at once, each one with its own
mail-sources and split-methods. There is one drawback however: you can't use
the respooling facilities across different backends.

-- 
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