MailEnable checks DNS blacklists in sequential order -- and this is generally fine when there are only one or two blacklists in use.
When there are many, such as when specifying multiple countries (China, Nigeria, Korea, Brazil, Malaysia, Taiwan, etc.) from blackholes.us, each blacklist query must time out before the next one is made.
If multiple blacklists are unresponsive, this results in the sender system timing out and giving up on delivery of the message.
Suggestions:
Mailenable should query all of the blacklists at once rather than waiting for each one to timeout before issuing the next query.
That way, the total timeout time would be no greater for all systems than it is now for just one.
Mailenable should log all DNS blacklist query timeouts in the SMTP activity log.
If a DNS blacklist becomes unresponsive, it will be obvious looking at the SMTP activity log.
Mailenable should be able to automatically disable a blacklist temporarily if it becomes unresponsive.
This should be user-configurable (number of timeouts, how long it is disabled before it is tried again, whether a message is sent to the postmaster informing him/her of the disabling of the blacklist, etc.).
Processing of DNS blacklists
I've considered that, but I don't know how to set up Bind on a Windows box and really don't want to learn -- unless it's trivially easy. I know that sounds lazy, but I've got too many other things to configure, administer, and keep updated. I did look at some shareware Windows DNS servers that look easier to set up and configure, though. But the real answer is for MailEnable to do parallel queries, which would really speed up mail transactions for everyone who uses it with multiple DNS-based blacklists.g_attrill wrote:For blackholes.us lists I would recommend setting up Bind on the server and run the zones yourself - this is much more reliable and you can even set up a custom zone and add your own IP addresses to block.
Gareth
