An A record assigns an IP address to a domain name. I believe the erroneous
"a:1.2.3.4" representation happens because people mentally interpret the RHS
of what comes after the ":" as that which is assigned to the A record: an IP
address.
The wizard that Microsoft sponsors:
http://www.anti-spamtools.org/SenderIDEmailPolicyTool/Default.aspx
asks the user to do exactly what you say is incorrect.
<Direct quote from the page>
Enter any additional IP addresses (or ranges of addresses) you wish to add to
your SPF Record (one address or address range per line).
Examples:
1.2.3.4
1.2.3.4/24
<End quote>
Furthermore, the correct way of using a, all by itself, doesn't work in this
wizard, even though a check box to designate it is present. The incorrect way
is cheerfully passed through to the end result, e.g. a:123.123.123.123
The wizard at http://spftools.net/create.php says:
<Direct quote from the page>
If there is another named host or subnet that can send mail from this domain,
enter it here, with the CIDR block size if appropriate:
(If you need to specify a host/subnet by IP address, please use an IP4 record)
<End quote>
Now, if you know the meaning, this may seem clear, but when I read it the first
time, not really understanding, I read it as an invitation to do exactly what
you are complaining about.
To be fair, this wizard did spit out an error after I entered an ipv4 address in
the box. The error message wasn't as clear as it could be, and showed up in an
odd spot.
Writing what you mean, in an understandable fashion, rather than what you think
you mean, is not an easy task. Before you complain that your users are dumb
clucks, take your words out into the cold light of morning and read them hard,
without your preconceptions turned on, to see if you really wrote what you
meant. Better, give your text to someone unaquainted with your meaning and have
them tell you what they read in it, Don't think they are dumb clucks if they
don't get it right. If several of your users can't, when they honestly try,
follow your directions to a working result, then you are the dumb cluck, not
them.
Mark Holm
mdholm(_at_)telerama(_dot_)com