On Sat, 20 Mar 2010, Glenn English wrote: > > Just why qmail reports a T_ANY failure as a CNAME failure, I also don't > know.
This is a bug in qmail. It tries to canonicalize domains in the SMTP envelope of outgoing messages. It originally did this by performing CNAME queries on each domain, but this caused interop problems with BIND 4. The CNAME query was changed to an ANY query, which is buggy in a number of ways: ANY queries are much more likely to trigger qmail's undersized DNS buffer bug; and ANY queries are supposed to be used for debugging not for normal operations. The correct way to canonicalize a mail domain is to do an MX query (or failing that A and AAAA queries) and if the domain is not canonical the response will include the CNAME record. The reason for canonicalization was conformance with RFC 1123 section 5.2.2. However when qmail was written this was not necessary for interoperability and the requirement was removed in the DRUMS process that yielded RFC 2821. So the way to actually fix the bug is to delete the canonicalization code. Tony. -- f.anthony.n.finch <d...@dotat.at> http://dotat.at/ GERMAN BIGHT HUMBER: SOUTHWEST 5 TO 7. MODERATE OR ROUGH. SQUALLY SHOWERS. MODERATE OR GOOD. _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
