From the way that the Security Manager at the other company describes it seems that they are choosing to block e-mail based on what amounts to the equivalent of IPNOTINMX for Declude.JunkMail. I was wondering if anyone would be willing to give me their take on what he wrote.
I'll be happy to give my opinion. :)
The IP address you had attempted to send the mail from is: 67.39.75.119.
The reverse address lookup for this IP address is: adsl-67-39-75-119.dsl.wotnoh.ameritech.net
The MX record for nexustechgroup.com is listed as: mail.nexustechgroup.com. 1H IN A 199.218.9.36
Our SPAM filter on our exchange server does reverse address lookups on inbound sender domains to ensure that the mail is coming from an authorized SMTP server for the sending domain. This appears to be the problem in why the mail never made it in here.
The administrator doesn't really know what is happening. The reverse DNS lookup is completely unnecessary to determine whether or not the mail was sent from an IP in the MX record (which probably means that they are running strange tests on the reverse DNS entry as well, which is likely to block a lot of legitimate E-mail.
As far as the IPNOTINMX part, the MX record specifies the mailservers that are authorized to accept *incoming* E-mail for a domain. There is nothing in DNS that allows a domain to specify which mailservers are authorized to send *outgoing* E-mail for a domain. And in real life, many legitimate domains send out E-mail from a mailserver that doesn't accept incoming E-mail for a domain.
The IPNOTINMX test was added to Declude JunkMail to *help* legitimate mailservers that are failing other spam tests. The idea is that if a mailserver does *not* fail the IPNOTINMX test, it is very likely to be sending legitimate E-mail. However, legitimate mail will fail the IPNOTINMX test for legitimate reasons (as opposed to the REVDNS test, where a lot of legitimate E-mail will fail the test, but not for legitimate reasons).
It is, however, acceptable for the remote mailserver not to accept your mail for almost any reason. On the other hand, given their too-strict anti-spam settings, they are intentionally not accept lots of legitimate E-mail.
-Scott
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