Outlook Sent folder not showing messages

Messages I send definitely arrive, recipients confirm, but my Sent Items folder stays empty or misses most of them.

IMAP account in Outlook 2019. Where do my sent copies go?

On IMAP there are two separate mechanisms that must both cooperate: Outlook must save a sent copy at all, and it must save it into the folder the server considers Sent. Either one misconfigured produces your symptom, so check both:

1

The saving switch: File, Options, Mail, scroll to the Save messages section and confirm Save copies of messages in the Sent Items folder is ticked. Unticked, copies simply are not kept anywhere, this is the blunt version of the problem.

2

The folder mapping: some providers keep sent mail in a folder named differently, Sent, Sent Messages, and Outlook may be saving into a local Sent Items while you look at the server one or vice versa. Look in the folder pane for a second sent looking folder under the account and check its contents.

3

Fix the mapping where the provider requires it: for accounts showing the option, File, Account Settings, double click the account, More Settings, and on the folders tab choose Save sent items in the existing sent folder on the server, selecting the provider's real sent folder.

4

Send yourself a test after each change and watch which folder receives the copy, that single test message tells you more than any settings dialog.

One more case for completeness: mail sent from a shared or delegated mailbox saves into your own Sent Items by default rather than the shared one, which reads as missing when you look in the shared mailbox. That behaviour has its own fixes server side, worth mentioning to your admin if any of the missing messages went out under another address.

Two sent folders under the account exactly as described, all my copies were in the other one. Remapped and the test message landed where I actually look. Months of confusion, one settings tab.