Up until about a week ago, I was able to send a group message with around 100 recipients.  Now, I get this error code:

Subject 'Meeting'
Server Error: 452
Server Response: 452 4.1.1 Maximum number of recipients reached
Server: 'smtp.windstream.net'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 25
Secure(SSL): No

What is the issue?  I have contacted my email provider and they said it was a Windows Live Mail issue.  Please help.