Joseph S D Yao wrote: > On 2013-10-18 04:46, Doug wrote: >> Hello, >> >> $ idig plus.google.com mx >> plus.google.com. 1200 IN CNAME plus-china.l.google.com. >> plus-china.l.google.com. 600 IN MX 40 alt3.aspmx.l.google.com. >> plus-china.l.google.com. 600 IN MX 50 alt4.aspmx.l.google.com. >> plus-china.l.google.com. 600 IN MX 10 aspmx.l.google.com. >> plus-china.l.google.com. 600 IN MX 20 alt1.aspmx.l.google.com. >> plus-china.l.google.com. 600 IN MX 30 alt2.aspmx.l.google.com. >> >> I never saw this type of MX. Are they valid records? > ... > > > Doug, > > This is fine. What would be bad is having a CNAME associated with the > other side: > > mail.domain.ex. MX 10 bad.mailer.ex. > bad.mailer.ex. CNAME real.mailer.ex. > > Cf. RFC 1912, 2.4 CNAME records.
while it's true that it is worse to have a cname used to link an MX to its target, it is not true that pointing a CNAME at an MX will nec'ily end well. in the above example, Sendmail in its default configuration will rewrite on the next hop the From: header so that it shows @plus-china.l.google.com. i think this is not the behaviour that google's trying to achieve here. and Sendmail may or may not be wrong to rewrite headers, but it's the default config, just the same. vixie _______________________________________________ dns-operations mailing list [email protected] https://lists.dns-oarc.net/mailman/listinfo/dns-operations dns-jobs mailing list https://lists.dns-oarc.net/mailman/listinfo/dns-jobs
