Rule #24
Do you know how to follow up an unanswered email?
  v12.0 Posted at 11/03/2014 6:39 AM by tiagoaraujo
Sometimes the person you send your email to may not reply immediately because they're busy or just may have forgotten about it.  If you need an answer, use a PING by doing the following:
  1. Reply to ALL
  2. Put (PING) in 1st line of the Body
  3. Plus any other instructions - such as "Hurry Up!" or "following-up, and looking forward to your reply" or "Need an answer please"​
Hurry Up
Figure: Good Example - (PING) written at the top of the email.

Of course you might use slightly friendlier language following up a client or a third party compared with following up a colleague!​ If it's really important and you need an answer you might like to consider using the phone instead of email​.