On Tue, 15 Sep 2009 11:12:52 +0100, Mark Goodge <m...@good-stuff.co.uk> wrote: > Dan Slay wrote: >> Thanks, that's what I have read. Which is why this make things more >> awkward. >> >> I cannot see that holding a recipient list is a solution. If, for >> instance, you relay for thousands of domains all going to different >> MTA's that hold each individual domains recipient list, its not really >> that straight forward and may impact performance? > > Postfix can generate and maintain an internal recipient list by means of > a recipient check on the downstream MTA before accepting mail to a > previously unknown user. See these pages for information on how it works: > > http://www.postfix.org/postconf.5.html#reject_unverified_recipient > http://www.postfix.org/ADDRESS_VERIFICATION_README.html#recipient > > Correctly configured, with the right degree of persistance in the cache, > this will have minimal impact on performance while also significantly > reducing backscatter. The actual tradeoff between effectiveness and > performance is dependent on how long data is cached for; if your system > can cope with it then it's best not to cache at all as that's the only > way to ensure zero backscatter. But even a fairly lengthy cache time > will be sufficient to prevent the majority of backscatter, provided that > the recipient email addresses don't get switched off very often.
One other minor issue with caching is when a mail is received for a non-existing mailaddress. The cache remembers this. When the mailaddress is created mail is rejected during the cache period. > > Mark -- YoungGuns Kasteleinenkampweg 7b 5222 AX 's-Hertogenbosch T. 073 623 56 40 F. 073 623 56 39 www.youngguns.nl KvK 18076568
