On Fri, 27 Jul 2012, Andrew McGlashan <andrew.mcglashan@affinityvision.com.au> wrote:
My experience is the exact opposite. I ran my mail server for years and never had any rDNS, then all of a sudden in a short period of time, lots of servers refused to work properly until I got my rDNS setup -- then no further problems. I do use a static IP from my ISP.
So, my experience is, that you MUST absolutely have rDNS to operate a mail server and not risk other mail servers "thinking" this is not a "real" mail server, so we can ignore them.
It may be helpful to have some reverse DNS entry, but you absoltely don't need to have any sort of meaningful entry. As has been proven by the list server we are using for this discussion the SMTP protocol name doesn't need to match the reverse DNS entry. In fact this server also demonstrates that you can have multiple A records with the same IP address without a problem. If you configure a server with a reverse DNS entry like 220-245-31-42.static.tpgi.com.au. (which my mail server currently has) then you can send mail anywhere (I run a bunch of servers on cheap TPG ADSL links for small companies, I get lots of complaints about all manner of email issue but never about reverse DNS). Anyone who checks for an existing reverse DNS entry but doesn't check that it's relevant is really stupid, I'm sure that there are people who are that stupid running mail servers, but they surely wouldn't be common. There are also probably some people who blindly copy config file snippets and accidentally have their server running in such a manner. But generally DNS entries don't matter. Even if you break SPF mail will be received by the vast majority of systems. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/