Can Mail modules provides simple load-balancing (round-robin and client IP) across backend servers?

[lhmwzy]

Can Mail modules provides simple load-balancing (round-robin and
client IP) across backend servers Like http HttpUpstreamModule?

upstream backend {
  ip_hash;
  server   backend1.example.com;
  server   backend2.example.com;
  server   backend3.example.com  down;
  server   backend4.example.com;
}

mail

{
 ......
  proxy_pass backend;
 .....
}