Using mailertable and DNS can load balance become redundancy?

Do you think is a good idea mix DNS with my Mail Exchanger Server (MX)
mailertable in this way?

DNS INTERNAL
InternalMailServerVirtualName=172.20.20.10=172.20.220.20 (Round Robin)

MAILERTABLE:
my.domain.org InternalMailServerVirtualName : 172.20.20.10 :
172.20.20.20

I think that with this configuration if one of the two servers is DOWN and
the other is UP, messages will be sent to the one which is UP and both I do
split equal traffic (50% each) to both. Is correct?

Plus: which parameter sets the time message is retried for each server when
mailertable is listened?

Thank You!
Leo.