Delegate is missing some emails in the sent folder belonging to the CEO (Outlook)

[Allinilla]

So this is a bit difficult to explan but a delegate for a CEO in our company, is missing certain mail in her "sent mail" folder (the sent folder belongin to the CEO.) 

It seems to be whether she opens the Outlook desktop version or the Web version, så perhaps not a sync issue.

when I ran a trace on one particular mail sent from the CEO (which the delegate can not se in the sent folder) I can see that the mail was delivered to the person it  was intended for.

we have added the CEOs mail box to the delegate in the account section in Ourlook and given permissions to the delegate (from the CEOs account). 

we have also designated the delegate in the CEOs account section.

generally the delegate, sees the mails sent from the CEO.

Has anyone here come across such an issue? 

[#2]

Perhaps those messages were marked as "private"? Have you selected the corresponding option when adding the delegate permissions?

[#3]

very good point :) is there any way from the O365 admin portal, maybe via message trace or something else, to see the status of the mails sent from the CEO? (in terms of them being marked as private and so on)

[#4]

No, that's an item level property, you cannot see it via the admin tools. You can use EWS or the Graph API, but it's easier to just ask the person :)