On Sun, 2011-07-17 at 21:57 -0500, Les Mikesell wrote: > Multiple interfaces, multiple IP addresses. Sendmail isn't going to track which > interface it is sending on and adjust its greeting. Sendmail ? Golly some of us have advanced to more advance systems like Exim ;-) When I complained to Cable & Wireless who operate mail sending from all the UK police forces, they adopted a seemingly unique solution by having the identical host name mapped to their different IP addresses. That solution solved it for me. > > Which type of 'cluster' were you thinking about ? > There are any number of topologies that use multiple IP addresses for what > appears to be one name. A load balancer might be involved, they may or may not > accept on the same IP's as they use for outbound connections, they may or may > not know the outbound ip. It is not inbound (to them) that interests me but outbound. Every IP address can have a host name, so in theory there is no reason for the use of fake (non-existent or wrong) host names when sending emails. When a computer application is configured to send emails, part of the configuration process permits a host name to be chosen. In theory there seems no sensible reason for a fake host name to be used and that must, I would have thought, apply to multi-homed, clustered, load-balancers etc. There is absolutely nothing to stop several IP addresses having the identical host name. > Just because it doesn't match the IP doesn't make it fake. There are three reasons why a host name may not match the IP address it is operating on. (1) there is no A record so that host name does not exist; (2) there is no reverse name for the IP address; (3) the host name belongs to a different IP address; > > Can you help me understand why bogus identities are necessary in these > > circumstances ? > You are the one defining it as bogus. Consider a system where one or more of > it's routes to the internet go through nat routers or the nat functionality of a > load balancer. The program sending the mail won't even know the IP you see. See my point above about configuring an application to send emails and the choice there is to use a genuine host name which belongs to the IP address that application is using to send emails. Bogus host names are simply a symptom of a disorganised and neglected mail sending (and perhaps also receiving) system where no one takes any pride in doing an important job responsibly. -- With best regards, Paul. England, EU.