Re: [cobalt-users] raq3 catch-all alias problems (& solution)

[Jeff Lasman <jblists@xxxxxxxxxxxxx>]

At 02:41 PM 2/16/00 -0600, you wrote:

> First, the text file /etc/virtusertable is converted into a Berkeley DB
> hash file, which doesn't have any notion of order.  If you try to step
> through a hash file, the order you get will be based on an internal
> representation, not the order the lines were in the original text file
> (or even alphabetical order).

Agreed.

> Second, sendmail's search rules go like this (in order):
>
> 1) If you have user@xxxxxxxxxx and domain.com is in the list of virtual
> domains, then lookup user@xxxxxxxxxxx  If you get a match, you are done.
> 2) If you have user+extra@xxxxxxxxxx, lookup user+*@domain.com.  If you
> get a match, you are done.
> 3) If you have user+extra@xxxxxxxxxx, lookup user@xxxxxxxxxxx  If you
> get a match, you are done.
> 4) If you have user@xxxxxxxxxx, lookup @domain.com, possibly replacing a
> "%1" in the result with the original user.  If you get a match, you are
> done.

I believe this, but I've never been able to find it.  I've always used 
"sendmail", the O'Reilly book, as Sendmail documentation.  After all, it's 
written by the same man who wrote the software.

Note that it all I've been able to find about FEATURE(virtusertable) is on 
page 274, and it does NOT say all this.  However, I agree that it IS how it 
seems to work.

> This set of rules is run repeatedly until none of the rules match.
> Rules 2 and 3 let you have "extra" stuff on the user part of an address
> and just strip it off to look up the virtual user entry.  After that, if
> user exists as a local user on the RaQ (even if they are not part of
> domain.com), the email would be delivered to them.
>
> The way Cobalt sets things up, virtual users are always setup only for
> @host.domain.com, not plain @domain.com.  If you check the "Accept email
> for domain" box, then a special entry like:
>
> @domain.com %1@xxxxxxxxxxxxxxx

This appears to automatically happen on the RaQ2; I don't remember setting 
up anything for it.

> is setup (this is the kind of entry that matches rule 4 above).  So, the
> rules get run twice: the first time turns user@xxxxxxxxxx to
> user@xxxxxxxxxxxxxxx, and then user@xxxxxxxxxxxxxxx gets checked.
>
> Now, on the RaQ1 and RaQ2, each user on a site had an entry in the
> virtual users file, even if the username was the same as the preferred
> email alias.  So you had entries like:
>
> user@xxxxxxxxxxxxxxx user
>
> So, for each user, rule 1 above would match, and then (since there was
> no longer a @domain.com part on the address) the rules wouldn't match
> any more.  So rule 4 was only reached for users that didn't exist.
>
> On a RaQ3, this is no longer true.  Users _don't_ get the alias anymore,
> so if somebody sends to user@xxxxxxxxxx, rules 1, 2, and 3, don't match,
> and then rule 4 matches the catch-all.
>
> That's why explicitly specifying an alias for each user that is the same
> as their username works, because then you put the
>
> user@xxxxxxxxxxxxxxx user
>
> line back in.

That's one reason why we don't use usernames as email addresses.

> Now, one other thing (and this is true for all RaQ products): since
> there is not an explicit
>
> @host.domain.com error:nouser User unknown
>
> line for each domain, users on a RaQ can (depending on what aliases are
> setup for a domain) receive email at any domain hosted on that RaQ,
> unless the domain has a catch-all.  For example, if you have dom_a.com
> and dom_b.com setup, and dom_a.com has a user "joe" and dom_b.com has a
> user "bob", AND dom_b.com doesn't have any user with an alias "joe",
> then dom_a.com's user "joe" will also receive email addressed to
> "joe@xxxxxxxxx".

This is the part I don't understand.  How do you figure?  Nevermind that 
since I don't use usernames as email addresses it doesn't matter, I'd still 
like you to step this through for me.

Thanks.

Jeff

--
Jeff Lasman <jblists@xxxxxxxxxxxxx>