When sending or previewing a message to your External Database Group if you get a message “Unable to determine size of Group” you should do the following :
Create a Query in your Database that returns the appropriate records/fields from the Database tables.
In GroupMail when creating the Group use the SQL
“Select * from Query” [Where ‘Query’ is the QueryName]
This will result in the recipient count being displayed in GroupMail.
[To modify an existing Group, simply go to Groups, right click on the Group and go to Modify].
Note : Do not use the “ORDER BY” clause in your SQL statement or you will get an error.
If you continue to have problems creating a new message in GroupMail after doing this, contact GroupMail support.