>They are sending thousands of emails that appear to be from:hotmail to >non-existent email accounts on my server. My IMGATE then goes to check if >that email does in fact exist in hotmail causing a dictionary/harvest >attack on hotmail.
reject_unlisted_recipient should come near the very top of restrictions. reject_unverified_sender should come at the bottom of restrictions. With the above order, the bad recipients are rejected before the senders are verified, preventing your problem. Note that SAV can kill your postfix if a domain's MX responds, but extremely slowly, so that the intitial in-SMTP-session SAV times out, causing a probe msg to be placed in the deferred queue. 10's of 1000s of SAV probes can kill server performance. Len
