primary    A     127.0.0.10
secondary  A     127.0.0.11
external   A     127.0.0.20

dodo       MX 10 primary
dodo       MX 20 secondary

# We need to use mx/8 because the source address will usually be 127.0.0.1,
# not 127.0.0.10 or 127.0.0.11.
# TODO: Once we support specifying a sender IP address, we should use that
# and remove the /8.
dodo       TXT v=spf1 mx/8 -all

kiwi       MX 10 external
kiwi       TXT v=spf1 mx/8 -all