DNS entry for SPF

[gregrjones at yahoo.com]

Can someone confirm that I have entered this DNS entry in correctly for
a txt record for SPF?

I have changed the names to fictious ones.

If I have coded this correctly, I should be authorizing servers with
hostnames of six.yada.com, 5.yada.com, ms1.ms2.yadastrett.com and a
server with IP address of 206.111.18.65 to send mail on behalf of the
domain:

"v=spf1 a:six.yada.com a:5.yada.com a:ms1.ms2.yadastreet.com
ip4:206.111.18.65 -all"

What would have been the difference with using this record vs using an
entry of "v=spf1 mx:six.yada.com mx:5.yada.com
mx:ms1.ms2.yadastreet.com ip4:206.111.18.65 -all"

Does MX: mean that the recipient server is to interpret each value
(following the "mx:") as a domain name and look up their MX records or
does it mean that each of these values must be in the MX record for the
domain name associated with the txt record?