Missing emails, Exchange 2013 on Premise , Outlook 2010, Barracuda SPAM filter

Hello,  I have a user that is reporting that she did NOT not receiving emails from a customer between 10-22-2018 and 10-24-2018.  
 I checked the spam filter and the customer is "whiteListed".

In the SPAM filter,  I can see all the emails that were sent to the employee from the customer as being "delivered" during this time frame.  

I then logged into the exchange 2013 server and did a delivery report and can see all the emails were delivered to the users mailbox from the customer during this time frame..  

But, if you login to the users mailbox using either Outlook 2010 or the OWA.  you can Not see any emails from this customer during that time frame.  I checked the deleted items, and also the "recover deleted items" and can't find any emails from this customer during that time.
  I also looked to see if she had any rules in her outlook client that might have moved the emails to a different folder and there is NOT any rules.....

where else can I look to find where these emails might have gone?

Thank you for your help.
Michael WilsonITAsked:
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Dean EgnerDirector of Professional ServicesCommented:
Did this happen for emails from a single customer or all emails during the time frame that is being researched?
Michael B. SmithManaging ConsultantCommented:
Look at her handheld device.

If Exchange says it delivered them - it delivered them.

Sounds like someone did a "permanently delete" to hide that they received the messages.
Michael WilsonITAuthor Commented:
Guys,  Thanks for responding so quickly.  
Dean,  yes all the missing emails from that time frame came from a single customer..  not sure if it was a glitch.  But the spam filter and the exchange server show hundreds of emails.
Michael,  as far as I know this user does not have email setup on her phone.  I’ll check with her on Monday.
I can retrieve the emails from backup and on the spam filter.. that’s not the issue.  What I am concerned about is where did the go?  The user said she got a call from the customer asking why she didn’t respond and that’s when the user reported that emails weren’t being delivered.  I checked the logs as stated in my initial post and saw that they did come in and were successfully delivered.. hope that make it a bit more clear.
Thank you.
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Hani M .S. Al-habshiContributor as IT ExpertCommented:
if successfully delivered
-Check exchange mail flow polices

-tray to forward emails from that customer to different  user .
-add the client  to exceptions on GFI ,anti virus,firewall,..etc
- check the sent items folder to see if they are getting forwarded automatically
- Search Mailbox
FOXActive Directory/Exchange EngineerCommented:
1.First check to see if the user has the mail set up on their phone.  Many of these phones with their default email apps have spam settings that will 'assume' certain messages are spam and filter them out as they please.  Check the spam setting of the email app on the user's phone.

2. In outlook do a search in "All Outlook Items" using either the senders name,emailaddress or the subject line that was used.

3. If the user uses webmail, open it up and check rules in their webmail as well.

If you have access to Exchange Management shell run the below commands

Get-MailboxJunkEmailConfiguration 'usersemailaddress'                        (check the blocked senders and domains)

Get-InboxRule -Mailbox 'usersemailaddress'  | Select -ExpandProperty:Description
Michael WilsonITAuthor Commented:
Guys, Thanks for your help.  Unfortunately, none of these suggestions shed any light on the solution.  I did run the powershell commands that  FOX shared and  I can see the cutomers domain name in the ALLOWED senders list.
Not rules are in the users mailbox.  the mailflow on the MX server only shows emails to be delivered to this users mailbox.
I logged in to the Users OWA and there are no rules in there either.  The users does NOT use OWA and does NOT use her phone to check email.

one thing I noticed is that all the missing (Hundreds) of emails have the same two subject lines and the same message body content.  I ran another report on the SPAM filter and it shows that all were delivered.  But, at the end of the delivery status it only shows it being delivered once...  
Here is a  the exported CSV file generated from the spam filter.  look at the Destination Server.   it only shows one entry.

I have a call in to the other companies IT dept.    The user from the other company says that the hundreds of emails is not normal.

maybe there was a glitch in one of the systems and only two email actually came through and the others are just anomalies?
Michael WilsonITAuthor Commented:
unable to find any indication that the user Did NOT receive these emails...  every log I look at shows they were delivered.  
closing this case.  Thank you all for your help.  moving on to the next fire... :-)

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Michael B. SmithManaging ConsultantCommented:
Hani and Fox provided you with support. They are due some points, in my opinion.
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