They will be in the senders sent items unless you enable this on your account:
If I authorize someone to send as me though Exchange Online will I see the sent emails?
shocko
100
Reputation points
Lets assume I am the owner of the mailbox "george@example.com" and via the Exchange Online administration I allow the owner of "john@example.com" to send emails as "george@example.com" while I am out of office.
Will those emails be stored in the folder of the "george@example.com" mailbox, or will they remain only in the "john@example.com" mailbox?Sent Items
I am currently using Office 365 with Exchange Online and I send/receive emails via Outlook 365 and Outlook online.