A user publishes new content to a group and a notification email is sent to group members. Sender is the username of the user who posted the content. However, the email address is the default address of the site. This is confusing as (at least my) users do reply to these emails thinking to contact the sender, but the email gets send to the site admin who has to forward it.
Also, having the username as the name of the sender can be confusing as members of large groups do not necessarily know the usernames of all members and could mistake the email for spam.
Match email-address and sender name to either admin of the site or the user who posted the content. This could be an option for the admin to decide as it would of course mean that the email address of the user is send out, so the default should be admin name and email address.