I run dual-stack IPv6/IPv4 networks, including mail servers. On occasion
I may not have IPv6 connectivity, but have IPv4 connectivity. When that
happens, I find that my mail queue accumulates mail that arrives over
IPv6, but cannot be sent out on an IPv6 interface.

(1) How to relay both IPv4/IPv6 outbound mail, regardless of whether it
came to the mail server via IPv4 or IPv6?

Is it possible to set up a relay action that works with either IPv6 or
IPv4, perhaps with a preference for one or the other?  I've tried
using "src <IPv4-addr>|<IPv6-addr>" on my relay action, but this
results in "No valid route to destination" errors (apparently due to
the name resolution on the smtp+tls:// URL returning the address from
the family opposite the selected src interface?).

I'd like inbound mail to come in via IPv4 or IPv6 and go out with a
preference for IPv6 but still work with IPv4 if IPv6 is unavailable.

(2) How to set up a secondary relay to use if a destination relay is

Is it possible to define multiple relay hosts in one action, or to
specify that a second relay action is to occur in the event of failure
of the first using match rules?

Jim Lippard        lippard-opensm...@discord.org       http://www.discord.org/
GPG Key ID: 0x99FD5CD6

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