On 2016-10-08, Always Learning <[email protected]> wrote: > > On Sat, 2016-10-08 at 14:06 +0300, [email protected] wrote: > >> Honest users send non-spam messages from dynamic IP-addresses. > > But do those "honest" (better: "genuine") users have:- > > (1) rDNS ? Probably not because it is a dynamic IP address with a host > name, if a host name actually exists, like > 123-123-123-66.dymanic.example.net > > > (2) A HELO/EHLO name which resolves to the IP address being used ? > Probably not. > > > How can the "honest" receivers of emails (MTA sites) distinguish (or > separate) the "honest" incoming traffic from the usual flood of > "dis-honest" traffic sent from the same range of IP address ? > > Why are "honest" users with dynamic IP addresses, unable to route their > outgoing email traffic via a smarthost or via a very cheap VPS running > MTA software like Exim ? VPS's usually have between 1 and 8 fixed, or > static, IPv4 addresses plus the ability to create DNS records such as A > and MX.
Honest users will be sending through a smarthost, so probably an 'a' in the 'by' clause unless they have some other arrangement with the smarthost, or the smarthost has a broken by clause. For this reason checking foreign received headers is a bad idea. As received headers can trivially be forged, they are unsuited to use in whitelisting. >> Those dynamic IP-addresses often are in blacklists. > > Because mail admins, like me for example, are unhappy at the vast amount > of spam originating from ranges of dynamic IP addresses. After a while, > we block hosts like You could just do what bt-internet does, and blaclist everyone, and only whitelist on request, but that may require additional staff.... -- This email has not been checked by half-arsed antivirus software -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
