dovecot - Aug 2005 - Dovecot Virtual Users & Sendmail

Not directly Dovecot, but a configuration problem.

We have a working set-up with Dovecot+Procmail+Sendmail, using 
POP-before-SMTP. We want to be able to offer email accounts to some 
local schools, using SquirrelMail (keeps their costs & maintenance 
down). The whole arrangement is working, but we don't want to have to 
have 300+ School children as users of our
Red Hat Enterprise server, so I've set up a passwd style file for 
authentication.

This all works fine, they can access mailboxes & send emails, but to 
receive Sendmail is checking that they are unix users & bounces messages 
back if they aren't in  /etc/passwd too.

Has anybody ever got Sendmail working with Dovecot virtual users?

Or is it time I switched to Postfix?

Chris Hogan

On Fri, 26 Aug 2005, Chris Hogan wrote:
> Has anybody ever got Sendmail working with Dovecot virtual users?
The problem is to help sendmail to find the backend to hand over the 
message. Usually sendmail figures this information for its own retrieving 
the data from the users database (passwd, LDAP, PAM, ...).

The only time I used non-existent, virtual users ever, I did something 
along the line of this thread:

http://www.mhonarc.org/archive/html/procmail/2002-12/msg00252.html

Setup the virtuser table to map each address into a paritcular unique ID, 
that is not clashing with any real user, then provide one alias per unique 
ID to file (or pipe) the message via aliases.

You should be able to generate this information from the fake /etc/passwd.

The mails are deliviered using the default UID (nobody, usually).
You can tweak this process by piping the message through a SetUID 
programm, but the main problem is that there is no way to figure out the 
recipient from the message passed into, hence, the recipient must be 
passed via command line, hence you need one line per user.

BTW: This is, more or less, the same way you integrate mailman into 
sendmail.

Another variant might be this (cf/README):

"
procmail        An interface to procmail (does not come with sendmail).
                 This is designed to be used in mailertables.  For example,
                 a common question is "how do I forward all mail for a 
given
                 domain to a single person?".  If you have this mailer
                 defined, you could set up a mailertable reading:

                         host.com        procmail:/etc/procmailrcs/host.com

                 with the file /etc/procmailrcs/host.com reading:

                         :0      # forward mail for host.com
                         ! -oi -f $1 person at other.host

                 This would arrange for (anything)@host.com to be sent
                 to person at other.host.  In a procmail script, $1 is the
                 name of the sender and $2 is the name of the recipient.
"

You should be able to make use of "$2", instead of re-sending the
mail.

Bye,

-- 
Steffen Kaiser

I would switch away from sendmail for sore. I like Exim the best.

Chris Hogan wrote:
> Not directly Dovecot, but a configuration problem.
>
> We have a working set-up with Dovecot+Procmail+Sendmail, using 
> POP-before-SMTP. We want to be able to offer email accounts to some 
> local schools, using SquirrelMail (keeps their costs & maintenance 
> down). The whole arrangement is working, but we don't want to have to 
> have 300+ School children as users of our
> Red Hat Enterprise server, so I've set up a passwd style file for 
> authentication.
>
> This all works fine, they can access mailboxes & send emails, but to 
> receive Sendmail is checking that they are unix users & bounces 
> messages back if they aren't in  /etc/passwd too.
>
> Has anybody ever got Sendmail working with Dovecot virtual users?
>
> Or is it time I switched to Postfix?
>
> Chris Hogan
>
>
-- 
Marc Perkel - marc at perkel.com

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