How can one differentiate between ill-suspicion and caution, and is feeling mocked or seeing someone acting suspiciously in front of the house considered ill-suspicion, and what is the extent of proof that justifies ill-suspicion?

Having a good opinion of people does not contradict being cautious of them. Allah commanded caution and forbade ill-suspicion, and the Prophet, peace be upon him, warned against suspicion. The sanctity of a believer is great, and it is not permissible to harbor ill-suspicion about him without clear evidence. A Muslim should have a pure heart, free from doubts and ill-suspicion, while also being cautious of what might harm him. A believer is discerning; he combines good opinion with caution. A person's feeling that someone is mocking him or lurking suspiciously around his house is not ill-suspicion if there is justification for it.