Client Authentication

[Lena at lena.kiev.ua]

> How about refusing to
> relay mail from addresses in a good DNSBL?

Bad idea. Legitimate users connecting from dynamic IP-addresses is normal.
DNSBLs list a dynamic IP-address permanently
or for long time after a zombied Windows spewed spam from it.
Some DNSBLs warn about that explicitly, for example:
http://www.spamhaus.org/zen/

| Caution: Because ZEN includes the XBL and PBL lists, do not use ZEN
| on smarthosts or SMTP AUTH outbound servers for your own customers
| (or you risk blocking your own customers).