When replying to requester the "To"-field is blank

When replying to requester the "To"-field is blank

Hi
 
As this it the first time we've encountered this issue, I didn't want to create a support ticket, as it is only a very minor problem.
 
We have 1 user out of 500 whom we experience this issue. Whenever I want to reply to a request raised by this user, the "To" email field is blank. Usually the requesters email will appear automatically. I can type the first name of the requester and then choose her from the list without any problems. This is easily something we can condone, but preferably we would like to fix it.
 
I compared the email settings of the requester with other users without finding anything to be different.
 
We are using SD+ 8.1.0 Build 8101 and Exchange Server 2010 with Outlook 2007.
 
Let me know if you have any questions.
 
Any ideas would be appreciated, thanks!
 
Regards,
Martin

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