When you send a Message, on the Prepare to Send Screen, Set Exclusion Options “Block All Recipients found in these selected Groups” if you select more than six Groups to Exclude it will return this error.
Solution for ‘The Group could not be opened as it no longer exists – 2409’
The workaround for this is to exclude less than 6 Groups.
That’s all there is to it.
If you continue to have problems after following these instructions, please contact the GroupMail support team. They will be happy to help.