On Thu, 18 Aug 2005, Steven Wayne wrote:

> >     I didn't know mx records couldn't be ip addresses....

RFC 1034:

  "The MX RRs have an RDATA section which consists of a 16 bit number     
  followed by a domain name."
   
RFC 974:
 
  "For the purposes of message routing, the system stores RRs known as
  MX RRs. Each MX matches a domain name with two pieces of data, a
  preference value (an unsigned 16-bit integer), and the name of a 
  host."

Note that, as a result of pressure long ago from a certain multinational 
company whose name starts with the digit 3, components of domain names 
are permitted start with digits. Thus, an IPv4 address is a 
syntactically valid domain name. A nameserver cannot therefore object to 
being told to load a record such as

  xxx  MX  1  1.2.3.4
  
because, syntactically, "1.2.3.4" *could* be a domain name. Sigh. 

-- 
Philip Hazel            University of Cambridge Computing Service,
[EMAIL PROTECTED]      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book

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