I figure some tips with setting up PowerMTA to mail TLD would help some people that aren't to familiar with PowerMTA or are set in their ways and might not have known about a certain feature. PowerMTA doesn't put IPs into back offs it puts VMTAs into back off. Setup each IP so it's in it's own VMTA. You do this so that way when 1 ip hits a backoff you can still mail on the remaining ips. For example you have 10 ips tied to 1 domain and you have 1 vmta setup to round robin over them they will all go into back off the moment 1 ip hits a TS01, DYN:T1, etc. Setup pools so you can round robin over the vmtas while feeding without having to complicate your feeder any more than necessary. Example: IP: 127.0.0.1 -> vmta1 IP 127.0.0.2 -> vmta2 IP: 127.0.0.3 -> vmta3 IP: 10.1.1.1 -> vmta4 IP 10.1.1.2 -> vmta5 IP: 10.1.1.3 -> vmta6 You want to use domains domain1.com, domain2.com, and domain3.com over vmta1 to vmta3 and domain4.com, domain5.com, and domain6.com on vmta4 to vmta6. setup a pattern list like this <pattern-list vmta-redirects> mail-from /@domain1.com$/ virtual-mta=127-0-0-x-pool mail-from /@domain2.com$/ virtual-mta=127-0-0-x-pool mail-from /@domain3.com$/ virtual-mta=127-0-0-x-pool mail-from /@domain4.com$/ virtual-mta=10-1-1-x-pool mail-from /@domain5.com$/ virtual-mta=10-1-1-x-pool mail-from /@domain6.com$/ virtual-mta=10-1-1-x-pool </pattern-list> If you have the pools setup correctly then all the mail from domain1.com, domain2.com, etc will round robin over all the vmtas listed in the pool and you won't have to worry about adding any extra headers (x-sender, x-receiver, x-virtual-mta). If you're using mailmerge then you'll still have to add all the junk that goes along with that in your feeder. Don't use backoff-reroute-to-virtual-mta, because you'll end up with all your mail in a single vmta causing you headaches. This wasn't meant to be an end all be all so if anyone wants to throw some more things out there please do. Post any questions as well.