blacklist

Is there a way to find the source of spam emails in cPanel? when I checked with mxtoolbox, my server IP is in email blacklist, it is UCEPROTECTL3 but I don't know why my server ip or my mail was marked as spam. Can anyone shoot me where to check or how to solve this problem?

When I check my IP with email spam blacklist at mxtoolbox then I see it is listed 1 time there (UCEPROTECTL3 ). I can not find a place to remove my IP from uceprotectl3 blacklist. Where and how to remove? can you guys guide me?

Today I can not send email to a person through my outlook, I checked my server IP with mxtoolbox and it got 1 blacklist on a network. My question is, How to avoid email blacklist for my server? and how to detect where sent email spam from my server to fix this issue for next time?