On April 22nd, 2014 AOL.com implemented a change to their email system linked to a policy titled DMARC.

DMARC stands for Domain-based Message Authentication, Reporting & Conformance and it is an email authentication policy that aims to prevent spoofing and spamming linked to the "From" email address on messages.
 
The change in this policy implemented by AOL means that any email message using a "From" email address of @AOL.com must originate from AOL's own email servers. Messages sent through any application outside of AOL itself, with a From address of @AOL.com will be rejected. These affected applications include ACTIVE Works® camps and Class Manager(or other ACTIVE Network applications).

To prevent future email messages from being rejected, please update your confirmation email, and broadcast email From settings to a different email address, other than AOL. Please refer to the instructions below to enable those updates.
 
To Update Your Confirmation Email:
  1. Login to your organizations Camps and Class Manager database
  2. Click Setup under your season
  3. Click Confirmation Email
  4. Click Edit on From field
  5. Enter a non-Yahoo email address
  6. Click OK
  7. Click Save and Continue
 
To Update Broadcast Email from Email Addresses:
  1. Login to your organizations Camps and Class Manager database
  2. Click Email tab
  3. Click Templates
  4. Select a Template
  5. Click Edit on the From field
  6. Enter a non-Yahoo email address
  7. Click OK
  8. Click Save