A message was sent to me with the address fields as:
To: “userj@domain1.com” userj@domain1.com
cc: userc@domain1.com, userk@domain1.com, “User M” userm@domain2.com
From: “User A” Usera@domain2.com
When I do a Reply To All, the fields become:
To: “User A” usera@domain2.com
cc: "userj@domain1.com, userk@domain1.com, “User M” userm@domain2.com
From: xxxxxx
Notice that the second cc field has a leading double-quote which is unmatched.