Trying to set up a bidirectional connection that source NATs all rserver initiated connections to the same IP as the inbound VIP.  I think I have the config right, but it doesn't seem to work.  The IP that should be used for all comms is a VIP of 172.31.0.176 which you will see in the NAT pool.  the 172.31.0.178 was created as a VIP for the rservers to send outbound to which will be source NATed to the 172.31.0.176.

rserver host RS_XXX_CORP_SMARTHOST_1
  description XXX CORP SMARTHOST FOR EMAIL
  ip address 5.5.5.5
  inservice

serverfarm host SF_EXC2013_SMTP_OUTBOUND
  description Exchange 2013 SMTP
  predictor leastconns
  rserver RS_XXX_CORP_SMARTHOST_1 25
    inservice

sticky ip-netmask 255.255.255.255 address source Sticky_SrcIP_EXC2013_SMTP_OUTBOUND
  serverfarm SF_EXC2013_SMTP_OUTBOUND
  replicate sticky

class-map match-any VS_EXC2013_SMTP_OUTBOUND
  description Exchange 2013 SMTP Outbound
  2 match virtual-address 172.31.0.178 tcp eq smtp

policy-map type loadbalance first-match EXC2013_SMTP_OUTBOUND
  class class-default
    sticky-serverfarm Sticky_SrcIP_EXC2013_SMTP_OUTBOUND

policy-map multi-match Farm_VIPS

class VS_EXC2013_SMTP_OUTBOUND
    loadbalance vip inservice
    loadbalance policy EXC2013_SMTP_OUTBOUND
    loadbalance vip icmp-reply active
    nat dynamic 6 vlan 511

interface vlan 511
  description ACE-DMZ-front
  bridge-group 1
  mac-sticky enable
  access-group input BPDU
  access-group input ANYONE
  nat-pool 6 172.31.0.176 172.31.0.176 netmask 255.255.255.0 pat
  service-policy input PM_AdminAccess
  service-policy input Farm_VIPS
  no shutdown