Reverse IP lookups

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Szerző: Philip Hazel
Dátum:  
Címzett: exim-users
Tárgy: Reverse IP lookups
I have changed the default configuration for the next release to contain

sender_host_reject_relay = *
helo_verify_nets = 0.0.0.0/0

It remains to do something about logging when the reverse lookup does
not agree with the HELO. I probably should have done something about
this a long time ago; consequently anything I do now is going to be
incompatible.

I propose, therefore, to put out the 1.71 release without any further
change, and to make a change for a subsequent release which will have
updated documentation etc.

Ultimately, I think there should be two variables: sender_host_name and
sender_helo_name. The first of these will be set to "?" if no reverse
lookup has been done, and the second to "" if no HELO command has been
received. The sender_fullhost variable will take several different
forms, depending on the values in the two base variables:

1. If sender_host_name == sender_helo_name, then it will look like

host.name [ip.address]

2. If sender_host_name != sender_helo_name, then it will look like

host.name (helo.name) [ip.address]

unless there hasn't been a HELO, in which case it looks like 1.

3. If there hasn't been a reverse lookup, or the lookup failed, then
it will look like

helo.name? [ip.address]

which seems to me to be a pretty good way of indicating some doubt about
the name. However, if there hasn't been a HELO either, then I think just
the IP address on its own is best.

Changing sender_fullhost will affect both the Received: header
and the contents of log files. The eximstats and exiqsumm utilities will
have to be updated to accommodate these. That's another good reason for
not rushing into this.

Views?

-- 
Philip Hazel                   University Computing Service,
ph10@???             New Museums Site, Cambridge CB2 3QG,
P.Hazel@???          England.  Phone: +44 1223 334714



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