It's not the first time I did this. Yesterday I had an interview, the company uses cakephp 2.x, CEO talked about how they suffer performance issues and how it's hard to scale and they really want a solution that can scale.
I came back home, did a little research, and then sent the hr an email today asking her to forward it to the CEO because I don't have his email.
My email contains a tool to help upgrade cakephp, some tips on performance and I remembered about phalcon framework which might solve their performance issues if they could somehow migrate.
Why did I do this? Because at the interview you talk a lot about different things, it's a conversation, so you forgot to say things which might help the other person. And after the interview, you get time to really understand the problem that the company suffers from and you have time to research and solve it. I couldn't find the cakephp tool, I had to google it for example.
And secondly, I believe that the world is a giant stackoverflow where it is my duty to help anyone if I know the answer, regardless of whether or not I get the job, here we are helping each other and expecting nothing in return.
Is it a habit I should stop doing or is it okay?