Hi hs2!
I think the problem might be with the "BaseColumnName" property. Just try removing this property and try. I am not sure about this but give it a try….
You have set "BaseColumnName" property to SendMail and u must be binding the data on each postback to display the data, right? So what i think is that the binding of checkbox column is overriding the current state of the checkbox. Say u have checked a checkbox, so its current state should be "True", but when u are hitting save button postback is happening and data is binding to it again and must be overriding the current state of the checkbox.
Just remove this property and check….
Regards,
Charuk.