A user sends a mass email to a group.
The user then goes into one of person records that received this email.
The user views this under the communication tab and then deletes the email.

The user then navigates to another person record that received the email but the email is not under the communication tab.

If the user deletes one of the emails all the emails for that group are deleted.

More information:

This issue is currently with development and will be resolved in a future release of Sage CRM.