> For improved robustness of a pre-queue setup look for Postfix 2.7.0 > with its "smtpd_proxy_options=speed_adjust" feature
Btw, the Postfix 2.7.0 also brings a feature which may be valuable to you: an outgoing MTA can have multiple IP addresses on its interface, and you can choose from which IP address a mail will be sent based on some criteria you establish to differentiate your customers. Postfix 2.7.0 release notes: - Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values. For example, let mail submitted by authenticated mail clients on a mail submission port go out on one IP address, then let mail from some trustworthy clients (small offices) with static addresses go out with a second IP address, and let the third IP address be used for everybody else. Eventually recipients may be able to assign reputations to each of your outgoing IP addresses, perhaps treating the first two more favourably or even whitelisting them, but certainly there will be less chance they end up on some blacklist. Mark
