Eric, Over the last couple of years working with qmailtoaster, I've come to both love and hate this particular CHKUSER check.
I keep copies of all the messages from the qmt list, and searching for the string "451 DNS Temporary Problem," it seems to me that people have many problems with it that could be addressed with some simple fixes to the CHKUSR code--e.g. more detailed error responses from CHKUSER that better define the nature of the problem. Unlike the posts I've read over the last year or so, I'm not having any trouble with my caching nameserver, DJBDNS. It's working properly, has always been working properly. I love DJBDNS. However, here's the problem that I have with this particular CHKUSER check: When a sender tries to send a message to a single "[email protected]," if the domain MX is unresolveable in DNS as follows: 2011-08-31 12:56:25.144555500 servfail nc-mail.nchicago.org. input/output error CHKUSR will return the "451 DNS Temporary Failure" error indicative of the issue. In this case today, the above particular domain has no MX record for it's e-mail--their problem, not mine. So, this immediately prevents queuing of messages in QMail that cannot currently be delivered immediately to that one particular domain. This is a good thing as it alerts the sender that the message cannot be delivered now--e.g. QMail is not going to queue the message now because it would just sit there, either waiting for the MX to become available or, if it does not, bouncing the message after the queuelifetime expires. Now, aside from the fact that the average person doesn't know what this means, I can deal with it, albeit it is not ideal (the average user-sender does not know what the heck "451 DNS Temporary Failure" is). However, when sending out a multi-recipient message, this is when the issue gets really dicey. CHKUSR stubbornly refuses to queue the message at all for any of the recipients, even the ones that have valid MXes, as it simply also returns the "451 DNS Temporary Failure" error with no other information at all. What this means is that the sender of the multi-recipient message has to figure out on his/her own which e-mail domain can currently not accept a delivery. The only way to determine this is to send the message to each of the recipients individually until you hit the one with the invalid/unavailable MX. Now, I think the ultimate resolution of this issue would be for CHKUSER to be updated to provide better error responses on this particular check. For single-recipient messages, it should respond with something like "451 DNS temporary failure: mail server for domain 'somedomain.com' is currently unavailable." In the case of multi-recipient messages, it should go ahead and queue the message for the valid domains, while returning a similar error for the MX domain(s) that is not available. Meanwhile, from what I can tell from the list archives, there is currently no way to disable this CHKUSER check entirely without manually recompiling CHKUSER. If there is already a simple fix/adjustment for this, let me know (and I'll apologize in advance for missing this). Otherwise, it would be great in future QMT releases to have this CHKUSER check disabled entirely, pending an adjustment to CHKUSER, as it results in lots of puzzled user inquiries. With this disabled, such messages would go into the queue for QMail to bounce on its own. I understand that the feature also alerts admins to their own DNS server issues as well. However, those should be issues that server admins can resolve on their own anyway. It's the user-related problems that this check causes that, to me, are most troublesome. Thanks! Tim -- Tim Pleiman Bravo Systems Technologies "Advanced Open Source Solutions for Business" Chicago, IL USA --------------------------------------------------------------------------------- Qmailtoaster is sponsored by Vickers Consulting Group (www.vickersconsulting.com) Vickers Consulting Group offers Qmailtoaster support and installations. If you need professional help with your setup, contact them today! --------------------------------------------------------------------------------- Please visit qmailtoaster.com for the latest news, updates, and packages. To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
