So i have this homework, i need to do a email client that sends emails, notifies when a new email arrives,etc.
One of my problems is verifying a domains reputation if the user writes an url in the body or subject of the email, if the domain can be danger i shouldn't send the email.  I tried mywot.com api, but i can't get a key to try coding.
I searched for other apis like domaintools, whoisxml, urlvoid but they have a ton of documentation, and i just get lost reading all of it, also they services are limited to free users.
Is there another api that i can try? o there's another way to valid user urls?
Thanks for your answers.
most of them are free until a certain number of queries are hit (like 1000 month). 
For a fully free API you'll probably need to implement it yourself, since indexing domain lists takes a lot of effort.
Check the free intervals of senderbase and virustotal
How to see Domains reputation with python?