Hi @ehyalera-1815 ,
Welcome to our forum!
Does this issue occur recently? If so, have you done any specific operations before that?
And do other users around you encounter the same issue?
Please first make sure the Save copies of messages in the Sent Items folder check box is selected via File > Options > Mail > Save messages.
On the other hand, as i know, the Save copies of messages in Sent Items folder option can be controlled using the Outlook Group Policy setting. Considering that the option is changed by gpo, it's also suggested that you could check the related settings in this article:
Outlook Group Policy setting
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