Re: [exim] Really Cool Trick

[catching up on list mail]

On Fri, Oct 20, 2006 at 12:03:21PM +0100, Ian Eiloart wrote:
> --On 19 October 2006 23:22:42 +0300 Stuart Gall <stuart@???> wrote:
> > On 19 Oct 2006, at 21:12, Martin A. Brooks wrote:
> >> Marc Perkel wrote:
> >
> > What he is doing I thing is getting exim to automatically create a
> > new account for any local part it receives on the domains it servs.
> > That is quite clever.
> > However, Marc, there is a huge problem (Assuming I read this right).
> > When the domain gets its first dictionary attack (sending spam to
> > loads of random local parts)
> > You will create hundreds possibly thousands of new mail drops.
>
> Yes, it would probably make more sense to use localpart suffixes, like this:
>
> foo+exim.org@???
> foo+amazon.com@???
> foo+itunes.com@???

I've been doing this at home for a couple of years now. Exim looks
up the domain of the recipient (say
"prefix-suffix@???") in a lookup file:

domain1.example: folder1
domain2.example: folder2

and looks up the local part (prefix before "-") in another file to
get the local user:

prefix: matthew

and then checks to see if ~matthew/Maildir/.folder1.suffix exists.
If it does then it delivers to this folder, otherwise it rejects
the recipient.

Have to be careful with folder permissions so that exim can read
all folders as the exim user. Did that by moving all Maildir
folders to /var/mail/username, and setting group and group sticky
bit like you might for mbox files. Exim does not auto-create
Maildir folders in /var/mail, which allows selection of which
accounts are permitted to receive mail.

Works great... create folder and e-mail address (at the right
domain) becomes live.

Matthew


--
Matthew Newton <mcn4@???>

UNIX and e-mail Systems Administrator, Network Support Section,
Computer Centre, University of Leicester,
Leicester LE1 7RH, United Kingdom