Sam Varshavchik has announced an updated release of the Courier Mail Server and Courier IMAP Server (Courier 20070921). Changes since the last release include

• A looping SPF query is an UNKNOWN result
• Ignore SIGPIPE errors in couriertcpd
• SqWebMail - remove some hardcoded settings. Use SQWEBMAIL_RANDSEED to force the random number seed for URL redirectors.
• Reject \<@domain.com> return addresses
• Include remote port number in IMAP and POP3 logs
• IMAP servers tries to autodetect clock skew