On 17 December 2011 20:11, Paul Welsh <paul at welshfamily.com> wrote: > For example, this works fine: > *.domain.com > - matches mail.domain.com, xxx.mail.com, etc Just thinking, if it's a domain like amazon.com then perhaps *.amazon.com is pretty safe. After all, I believe Exim does a reverse lookup on the IP to retrieve the hostname.