Hello ds_2023,
Thank you for reaching out to Apple Support Communities.
These steps should help to disable the filter:
"Filter emails
- Tap
in the bottom-left corner of a mailbox list. - Tap “Filtered by,” then select or turn on the criteria for emails you want to view.
To turn off all filters, tap
. To turn off a specific filter, tap “Filtered by,” then deselect it."
More details can be found here: Filter emails in Mail on iPhone
If the issue persists, can you provide a few more details? Does this only. happen with one account? When did you first notice this? Also, what is your exact iOS and iPadOS versions?
Cheers!