Hi,

In experimenting with a different mailserver, I set it up as a proxy, 
connecting to Courier via SMTP to a) do an existence check on the 
recipient and b) deliver the mail if that check was succesful.

In doing this, I ran into the MAXPERIP/MAXPERC limits that I'd given 
Courier, so Courier would start refusing connections.

In checking the courier and couriertcpd manpages and experimenting with 
smtpaccess settings, it looks like those environment variables are not 
available from smtpaccess.

For this sort of scenario, where trusted ranges create a lot of 
connections, it would be useful to be able to override MAXPERIP/MAXPERC 
on a per-ip or per-cidr basis via smtpaccess.

The upper limit for proxied connections would then become MAXDAEMONS, 
which seems reasonable to me; trusted ranges would then receive priority 
over less-trusted hosts in assigning resources. The MAXDAEMONS limit 
would then still protect the server against SMTP/TCP DDoS attacks.

A feature like this could even be used to throttle down the available 
resources for specific ranges known to be spammy (e.g. the end-user 
ranges of known-bad providers, or 'all the Chinese IP ranges I can find'.

Is this possible in the current courier architecture?

I realize there's several workarounds I can use to achieve my current 
goal, including delivering the mail via the MSA and give that higher 
limits; and upping the MAXPERIP and MAXPERC limits to something above 
MAXDAEMONS (which works for me for now).

Regards,

Vincent.

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