Currently, the notification system allows:

• Getting browser desktop notification for any activity
• Getting email notification for mentions

I'd like to have the mix: get email notification for any activity when I'm not logged-in. Many systems allow this (eg. gitter's "You have unread messages" emails), but I couldn't find it in Mattermost.

Ideally, the system would :

• Wait a few minutes before sending the notification, to send a mail containing several messages at once.
• Send only one notification even if there are further messages, to avoid flooding the mailbox with tons of emails

This would be very useful to follow low or medium traffic channels.