Declude does a seperate DNS lookup "for each IP4r test for each email" it is set to check. So if you do 12 different ip4r type tests, 12 DNS queries are done for each email. Declude either uses the DNS server you hand code in global.cfg, or it uses the one defined in Imail's SMTP tab.
Correct.
Declude does NOT cache any results from these lookups, but the DNS server
that Declude references DOES cache these lookups - just like any other DNS
lookup - up to it's TTL. Most DNS servers will cache both positive ("I
found an answer") and negative ("no answer was found at the DNS server")
results.
The one catch here is when a single E-mail results in two or more identical queries (for example, with the OSSRC, OSFORM, OSRELAY, etc. tests). In this case, Declude JunkMail makes 3 identical queries (in this case, all would be "1.0.0.127.relays.osirusoft.com", if the IP was 127.0.0.1), which the DNS server may end out 3 times (even though it only needs to be sent out once). The next release of Declude JunkMail will only send out 1 query in this case, which will cut down on DNS traffic slightly.
If your DNS server is local - and your declude is busy - your local DNS server will have a rich cache of recent lookups it's already done. relays.osirusoft.com's default TTL is 2 DAYS. That means unless you set a lower TTL in your resolver, if you recieve 1000 emails from a certain spammer IP within that two day period, your server will answer 999 of the queries from it's local cache. Declude does not cache, but if a good percentage of Decludes lookups only involve your 100/1000 LAN (and not external lookups over the Internet) - performance will greatly improve.
Correct. And a very good explanation, by the way!
-Scott
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