I recently started getting the message below to one of the groups we have set up.  it has been a group for a long time - but had a few new names added to it. 

"Please use the following format for email addresses: *** Email address is removed for privacy ***. If you're using category names or nicknames, make sure you don't have any typos.
Possible typos: r"

When I look at the group it says the group name and then "271 of 273 members."  Is the problem the size?  We only added a few names recently (maybe 20) but have no way of knowing who they are without a labor intensive search

Ideas?