Cannot send mail to a couple of users in house

I have a client that has  one workstation that cannot email to two in house users.  All other in house users can email the two. They are using pop accounts at the workstations and exchange for in house calendaring.  In the nickname cache where you begin to type the users name I have deleted the two users from the cache to see if their names were corrupt but that did not make a difference. Any ideas?
captjcretAsked:
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Axis52401Security AnalystCommented:
What bounce back message are you getting?
captjcretAuthor Commented:
From: System Administrator
Sent: Monday, September 22, 2014 3:53 PM
To: Stephanie Martino
Subject: Undeliverable: COUNTY OF LOS ANGELES - QUARTERLY REPORT IS DUE


Your message did not reach some or all of the intended recipients.

      Subject:      COUNTY OF LOS ANGELES - QUARTERLY REPORT IS DUE
      Sent:      9/22/2014 3:53 PM

The following recipient(s) cannot be reached:

      'Deborah Kimball' on 9/22/2014 3:53 PM
            None of your e-mail accounts could send to this recipient.

      'Raffi Jaltorossian' on 9/22/2014 3:53 PM
            None of your e-mail accounts could send to this recipient.
Mark GalvinManaging Director / Principal ConsultantCommented:

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captjcretAuthor Commented:
Rebuilding the profile
captjcretAuthor Commented:
Rebuilding the profile did the trick
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