wie...@porcupine.org (Wietse Venema) writes: > Dave T?ht: >> wie...@porcupine.org (Wietse Venema) writes: >> >> > Dave Taht: >> >> So what I think I want to do is setup fallback relaying as follows: >> >> >> >> MX 5 mylaptop.example.org # if my laptop's up send mail there >> >> MX 10 mytinyarmbox.example.org # if not, try my arm box >> >> MX 20 mysmarthost.example.org # otherwise, default to my well connected >> >> host >> > ... >> >> Problem 1) I am under the impression from a foggy memory of reading some >> >> RFC or other, that at minimum, 2 MX records will be tried. So adding a >> >> third might introduce problems with some MTAs that ONLY do 2 MX records, >> >> in that far off day when more stuff speaks ipv6 directly, or when it >> >> fails to fallback to my third, primary smarthost. >> > >> > SMTP is defined in RFCs and the ones concerning SMTP are RFC 821, >> > RFC 2821, and RFC 5321. By now, most mail systems in existence will >> > be build after RFC 2821, which says "the SMTP client SHOULD try at >> > least two addresses". With three MX hosts you're operating outside >> > the recommendation. >> >> Many hosts seem to have more than 2 MX records. Gmail, for example, > > Unlike your unsupported configuration, gmail etc. do NOT require > that a client tries MORE THAN TWO addresses. > > Wietse
I implemented bind9 views to present 2 MX records to the world, and 3 to my internal servers, with multiple smtp_fallback_relays as per your suggestions. Postfix is smart enough to figure it all out. The tiny arm box is working well now. Most of my remaining problems re email are DNS related and not relevant to this list, so I have been making updates to my blog regarding this project and the problems I've made for myself. Thanks for the help! -- Dave Taht http://the-edge.blogspot.com
