Exchange 2016 Enterprise, about 600 users, tons of free RAM and disk on server.
Unusual event for a single user. Beginning around lunchtime on Friday, user stopped receiving new emails in Outlook and iPhone. Outlook inbox showed no new messages. The mail app icon on the iPhone showed an increasing number of unread messages, but when she viewed the inbox, just like she did in Outlook, no new messages were seen.
Others began calling her on Monday asking why she had not responded to the Friday emails. Employee said she never received them. Senders re-sent the same messages and they arrived immediately.
Then... the next day (Tuesday) all of the "missing" emails from Friday suddenly appeared in Outlook and the iPhone.
I dug through the Exchange logs and traced each missing message. All of the originally delayed emails showed DELIVERED to the...
