This issue is being discussed here:

If everyone is OK with it, the solution will be as follows:

The problems we have been experiencing with people complaining about email notifications have been identified as associated with groups that have too many messages.

There is just one group in this category: the CAN group.

(The CAN Exec Group could be in this category, but let's re-evaluate again after sorting out the CAN Group)

Ideally, what we would like to have is the following behavior:

- By default, all users are able to set email notifications selectively by group. This should clear and easy for every user. 

- By default, email notifications are set to "Send  Email" for  all users.

The above applies to all groups, except for the CAN Group, which should be configured as follows:

- By default, all users are able to set email notifications selectively by group.

- By default, email notifications are set to "Do not Send  Email" for the CAN Group.

Other groups may be treated the same way as the CAN Group, to be decided on a case by case basis.