Just checking back if there is recommendation to increase outbound mail delivery .
On Fri, Jan 26, 2018 at 11:04 AM, Stephen Satchell <l...@satchell.net> wrote: > On 01/25/2018 05:58 PM, Viktor Dukhovni wrote: > >> This is not good advice, it breaks delivery to other domains. Much better >> to run a local caching resolver. Note also that the OP reports that >> raising >> concurrency does not improve throughput by much. If DNS lookups were slow >> higher concurrency would lead to a significant throughput increase. >> > > +1 > > In the dim, dark past, when I was mail administrator for a hosting > company, I configured a PostFix instance (bare metal, not VM) that > smart-hosted (I'm guessing) 40-50 instances of qmail and exim in Web > control panel systems. The outgoing mail volume was on the order of tens > of thousands per hour. (That server did per-domain throttling for the > major mail services, to avoid being nailed by the traffic monitors on those > services.) At peak outgoing load, it still loafed. > > On that outbound MX server, I configured a local caching DNS server. The > key to success was to configure the size of the memory cache up and up and > up. That limited the number of recursive look-ups that had to go > off-system. > > For the incoming MX (on a separate box) I did something similar, yet > another local caching DNS server, to ease the DNS resolver traffic for > PostFix, DNSBLs, and spam assassin. > > The reason I don't recall the actual size of the CNS cache is that I > "tuned" the size of each DNS cache until the amount of outbound query > traffic was acceptable to me. Neither box had minimum hold times set up, > so it didn't do all that much for domains with short (~300 seconds or less) > hold times, but those were a small percentage of the look-ups that were > cached. > > N.B.: Before doing the smarthost consolidation, my main DNS servers were > running at red-line. >
