Symptom:
Users sending emails in Outlook or on a mobile device connected via ActiveSync or Outlook Anywhere reply all to an email message. The sender ends up also being copied on the reply as well as having it show up in the sender's Sent Items.
The user mailboxes are on 2013 and also use Lync 2013, so they have SIP addresses in their list of valid PrimarySMTPAddress values.
How can we prevent the sender from getting copied on messages they "Reply All" to? This doesn't occur when connected via OWA.