We host the DNS and website for a client but they have their mail server at their location. We have an SPF record setup for them which has never given us a problem in the past.
SPF record: v=spf1 mx a:exchange.clientdomain.co
We have an mx record = exchange.clientdomain.com
We have an A record = 184.108.40.206
Now, when one of the users sends an email to a yahoo address with a group of other people, she is receiving a softfail error:
"Message from yahoo.com.
Unable to deliver message to the following address(es).
This user doesn't have a yahoo.com account (firstname.lastname@example.org) 
--- Original message follows.
The original message is over 5K. Message truncated.
Received-SPF: softfail (mta1039.mail.re4.yahoo.co
m: domain of transitioning email@example.com does not designate 220.127.116.11 as permitted sender)"
Now, she can send an email to this yahoo address individually and it works w/o a hitch. I'm new to DNS so help is greatly appreciated. BTW, I did not setup the SPF record, it was in place when our DNS guy left. I tested in http://www.kitterman.com/spf
and here is what I get, which baffles me even further because their other tests passed for the same record:
"SPF records are primarily published in DNS as TXT records.
The TXT records found for your domain are:
"v=spf1 mx a:exchange.clientdomain.co
SPF records should also be published in DNS as type SPF records.
No type SPF records found.
Checking to see if there is a valid SPF record.
No valid SPF record found of either type TXT or type SPF."