The sender address verification sends an HELO *before* the receiving server emits its SMTP banner. Thus, the probe (or the whole server) gets classified as "earlytalker" and (in my case) gets disconnected immediately. The verification probes must adhere to the SMTP protocol, otherwise they're worthless because they're generating false negatives.
2009-07-01 09:38:30 UTC in Smart Sendmail Filters
