Hi @MarcoMandricardo-1414 .
- Where did you search in Outlook client? I did not find the search bar you used in Outlook 2016. If you could, please share how you searched it.
- If you use "From" and "To" to search for email items in this mailbox, will this problem also occur?
- If you could, please try to use “From” and “To” to search for email items in outlook cache mode.
- Please try to search email items by using “Advanced Find” in outlook client. Search by "From" and "Send To".
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