some sent emails are missing and moving to "recover deleted items"
hello , we are using on-premises exchange server 2016 in my environment. and we are using microsoft outlook 2019 & 2021 . i have one question : i notice that the sent emails for all users are appear in "recover deleted items" , however these emails are not deleted and still exist in sent items folder . so it is appear the same emails in "sent item" folder and in "recover deleted items" , which i think very weird . i have one incident : one of my user is encounter a weird problem , that some sent emails are weirdly disappear from "sent item" folder but he never delete them , and we can found these items in "recover deleted items" , but the restore option in "recover deleted items" didn't restore the email to the user mailbox . however i don't have any problem mention in healthreport for my exchange server , all in good condition . what may be the problem ?