Actually I do not need to see the blocked notice, I know what the problem is. The problem here is that you are sending to too many people.
Yahoo mail is not meant to be used for email marketing to email blasts to large groups. It is really meant as a personal email system.
There is no way I can unblock this for you. Yahoo has automated rules for email accounts and if your account is violating those it will automatically be blocked.
You have a couple of options.
You can request that you be allowed to send emails to groups but you will need to submit a request to the yahoo post master by filling out this form:http://help.yahoo.com/l/us/yahoo/mail/postmaster/bulkv2.html
Filling out the form would be the first thing you should do.
If they deny you or you do not meet the requirements necessary for sending bulk email then I would suggest you use a proper email service to send your mail.
The reason you should use a proper email service is because not only will yahoo block you from sending but the recipients email servers may blacklist you as well because they can tell a large amount of mail is coming from a personal yahoo account which could set off their security measures.
It is best that if you are sending to a large group you use a service. There are many out there. One free one that works well is mail chimp. http://mailchimp.com/pricing/
They allow you to send up to 10,000 to 2000 subscribers per month for free.
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