Victor Duchovni: > On Fri, Mar 19, 2010 at 06:08:12AM -0600, Glenn English wrote: > > > It looks to me like the problem has something to do with DNS, not > > SMTP, right? > > Yes. > > > And why would Yahoo be doing a CNAME lookup? > > Their MTA does that for all destinations, among other lookups. > > > (I checked > > from a remote site -- my domain's MX server's IP is an A, and I don't > > see anything having to do with CNAMEs in 'host -t MX slsware.com'.) > > Your DNS server is a bit odd: > > $ dig +trace -t any slsware.com > > ... > slsware.com. 172800 IN NS ns1.richeyrentals.com. > slsware.com. 172800 IN NS ns1.slsware.com. > slsware.com. 172800 IN NS server.slsware.com. > ;; Received 148 bytes from 192.5.6.30#53(A.GTLD-SERVERS.NET) in 46 ms > > ;; connection timed out; no servers could be reached > > While asking for "cname" or "mx" works... Perhaps their code does a > "T_ANY" lookup.
If I recall correctly, Yahoo runs a modified qmail, and indeed: int dns_cname(sa) stralloc *sa; { int r; int loop; for (loop = 0;loop < 10;++loop) { if (!sa->len) return loop; if (sa->s[sa->len - 1] == ']') return loop; if (sa->s[sa->len - 1] == '.') { --sa->len; continue; } switch(resolve(sa,T_ANY)) { case DNS_MEM: return DNS_MEM; case DNS_SOFT: return DNS_SOFT; case DNS_HARD: return loop; default: ... } } return DNS_HARD; /* alias loop */ } Wietse