Dave T?ht:
> 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.
> Problem 2) My smarthost is only smart enough to try sending to one other
> relay (I think).
If the machine sends mail to a less preferred MX host than itself,
then it is badly borked. To pull that off with Postfix you would
have to turn off DNS or override the routing with a transport map.
Wietse
