On two separate occasions now, I've found that Exim (2.05) will reject a
connection from a machine if that machine doesn't have a reverse DNS entry.
Unfortunately, the connection is rejected with no fanfare and nothing about
the event is written to the logs.
>From what I've seen, the connection from the machine that has no reverse DNS
entry is rejected before Exim sends the SMTP banner. So all they see is
something akin to:
% telnet mail.europa.com smtp
Trying 199.2.194.10...
Connected to atheria.europa.com.
Escape character is '^]'.
Connection closed by foreign host.
In the first case, the machine being rejected simply didn't have a reverse DNS
record. In the second case, there were two A records pointing to the IP
address of the rejected machine. Therefore, one of the machine names for that
IP address was "robbed" of a reverse DNS address.
For example, MAIL.DOMAIN.COM and SLAPPY.DOMAIN.COM both were A records
pointing to 127.33.22.11. Looking up MAIL.DOMAIN.COM returned 127.33.22.11.
Looking up 127.33.22.11 returned SLAPPY.DOMAIN.COM. Which, I'm guessing,
confused Exim enough to make it close the connection before sending the SMTP
banner.
Like I said, this has only happened on two occasions, so I'm not entirely sure
that the assumptions I've made are fact, but it seems to be at least somewhat
true.
Has anyone noticed this besides me?
Thanks!
--
Robert C. Zilbauer, Jr. Europa Communications Inc
Primary: zilbauer@??? Secondary: zilbauer@???
"Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn."
--
*** Exim information can be found at
http://www.exim.org/ ***
