Yes Matthew, you are correct in guessing that I have the Connecting Host options ticked and if I was confident that I could drop all senders lacking rDNS then it would be a simple matter to clear the settings here and move them to my BLACKLIST group. However, inspection of the No Domain Information line of my Incoming Mail report suggests that this would be unwise.
I'd therefore like to handle this type of mail at either the message filter or content rule level, combining the lack of rDNS with other factors I can identify. I'd previously read article 117977 and also discovered the $HATentry variable in one of the guides, but none of the variables I've found appear to be what I'm after in this particular scenario. I've been testing the values by inserting them into headers.
$group: doesn't appear to work. Filters return "$group" rather than any resolved value. Reading the guides I'm wondering if it would return a matching entry from the sender list added manually to a group, but I haven't tested for that.
$HATentry: only good for SMTP replies, it seems. I get "$HATEntry" from my tests.
$policy: gives the mail flow policy, complete with a dollar sign on the front that might cause problems later.
$remotehost: returns the host name if resolved through a PTR and $remoteIP if there is none, rather than indicating the NXDOMAIN or SERVFAIL outcomes I'm after.
$remoteIP and $reputation: work consistently
It occurs to me that I can get the result I want by creating a sender group with no associated SBRS purely for dealing with the Connect Host DNS Verification results and then read the corresponding $policy variable, but instinct tells me this would clutter my HAT. I'd prefer to find a variable I can interrogate directly. If it's more efficient to add HAT entries (and Incoming Mail Policies as is advocated in 118551) then I'd best accept that rather than trying to keep these tables compact and neat on top of a long list of content rules and obscure message filters.
I should have mentioned earlier - I'm on Asyncos 8.5.6-074.
