2009/6/16 Terry L. Inzauro <[email protected]>: > I like the idea of verifying addresses, but this stuck out. > > > <snip from the "Postfix Address Verification Howto"> > > WARNING > > The sender/recipient address verification feature described in this document > is suitable only for low-traffic sites. It > performs poorly under high load; excessive sender address verification > activity may even cause your site to be blacklisted by > some providers. See the "Limitations" section below for details.
I think this warning really applies more to the wider internet, as opposed to infrastructure that you maintain/own/control yourself. In short, people don't like extra traffic. Sender/recipient verification is extra traffic. Recipient verification is usually discussed for exactly the situation you're in; you only perform recipient verification for domains that you accept "inbound" mail for, and only because you can't get an address list ahead of time. Obviously it's silly to be blacklisted by your own downstream MTA, it's assumed you're whitelisted because you're a backup MX.
