Qmail has an undersized 512-byte buffer to receive a DNS response, when in reality a real response can be up to 65536 bytes. When delivering email to a site with a large MX record, such as aol's, the qmail-send log will log a temporary error of "deferral: CNAME_lookup_failed_temporarily._(#4.4.3)/", and attempt resending. Eventually messages will make it through, but it will cause a delay of several hours. A patch exists that properly extends qmail's buffer, and is available at http://www.ckdhr.com./ckd/qmail-103.patch. I've tested this patch on my mail-mta/netqmail-1.05-r8 (via QMAIL_PATCH_DIR), and ran it successfully without problems. I would hope that this patch be officially folded into the Gentoo ebuild as qmail will probably not see an update this century, and this very dramatically affects the performance of the mail server. Reproducible: Always
Use QMAIL_PATCH_DIR if you want this.
Shouldn't this be consider implemented? Even root servers are going to move to >512 bytes responses in UDP with time (has started as move over to ipv6).
