Its a known issue. Your IT Dept can confirm in the 365 portal:
EX437337
October 24, 2022 3:51 PM
Title: Some users' outgoing email messages on Outlook on the web may be saved in the Drafts folder instead of the Sent folder
User Impact: Users' outgoing email messages on Outlook on the web may be saved in the Drafts folder instead of the Sent folder.
More info: The email messages are successfully sent but appear in the Drafts folder after sending. The impact is specific to them not showing in the Sent folder as expected.
Current status: Our review into the potential memory corruption is ongoing while working with affected users to further isolate the specifics of the change that resulted of impact.
Scope of impact: This issue may impact some users sending email messages through Outlook on the web.
Start time: Monday, August 22, 2022, 10:03 AM (2:03 PM UTC)
Root cause: A recent update to Outlook on the web service components contains a code issue, causing messages to be sent as expected but not moved out of the Drafts folder.
Next update by: Thursday, October 27, 2022, 4:30 PM (8:30 PM UTC)