If you operate a legitimate mail server, please file a request to have your IP address listed at DNSWL.org. If your buddy's MTA IP address is not listed, suggest that they get themselves listed. DNSWL is useful for multiple purposes like:
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- Spamassassin adds a negative score if the sending IP address is listed in DNSWL. This can be both good and bad in different ways, but recent measures indicate that it makes almost no difference to spamassassin's determination. This is because spamassassin is carefully balanced, and DNSWL is rarely wrong. If you do see cases where DNSWL is wrong, please report it.
- Some major servers utilizing greylisting use DNSWL as a means to avoid greylisting for "known good" IP addresses. This eliminates delays during delivery of mail from your server to other servers.
- Some DNSBL's use DNSWL as additional input in their reputation decision. Not exactly a "stay out of DNSBL" pass but it does help, assuming you really are not sending spam.
