According to ReturnPath’s newly released Q2 2008 reputation benchmark report, properly configured MTAs are over 200% more successful at delivering messages.
The report studies a significant sample of email messages received by ISPs and their ultimate outcome i.e. delivered, filtered, rejected, etc.
The report underlines how important it is to have a properly configured mail server. In the report improperly configured email servers are classified as Illegitimate and, according to ReturnPath’s data, these illegitimate (improperly configured) servers have a delivery rate of less than half of that of properly configured servers.
This report is very insightful, 5 pages, and includes great colorful charts. I would highly recommend it to any email sender.
You can get the report here.