On Wed, 24 Oct 2001, Kirk Friggstad wrote:
> Hello Davide (and everyone else):
>
> I've just been through a few days of hell with XMail 1.10 on Linux. For the
> past few days, XMail has been consuming an excessive amount of CPU time,
> sometimes even bringing our system to a halt. It turns out that it was
> caught in a loop - here's what happened:
>
> For one of the domains we have hosted ("xyz.com"), there is only one user
> account (named "default"). This account has the "*" alias assigned - it
> receives mail for any address in the domain - and redirects that mail to an
> external address. The problem began when someone changed the forwarding
> address to "[EMAIL PROTECTED]". Can you see where the loop starts here? It's
> like a denial-of-service attack by XMail on itself - really interesting to
> watch in debug mode...
>
> Is there any way to detect this type of mail loop inside of XMail? It might
> not seem like a big deal, as most administrators are smart enough to not
> create this type of setting (unless they're seriously sleep-deprived like I
> am), but there are a lot of third-party admin screens that are allowing
> users to go in and change their forwarding settings, etc. by themselves, and
> possibly creating this problem on their server.
The problem arises coz no SMTP gateways are involved inside the loop, it
happens all inside XMail. Mail looping between MTAs is handled by XMail.
By adding internal loop cheking would mean add extra headers that would
lead to rewrite the message file every time.
This will impact the overall XMail performance and i'm not willing in
doing this kind of fix.
But this could be a valid entry for the troubles section of the
documentation project :
Q: My server is eating all my machine's CPU cycles. Why ?
A: Check your internal redirect :)
- Davide
