I work in a team of several people. Officially we are responsible for different parts of a process. Which means that we sometimes need information from one another.
One of my colleagues doesn't give me information. His normal answer when I ask him for something is "I don"t know" (although it's a question that pertains to his part of process) or "ask X, I would too" (although the colleague and not X is responsible for that) or "it's not the technology I'm a specialist in" (he's responsible for all technologies related to his part of the process) or simply ignoring me. These are questions I need to clarify as they have strong consequences for my work. I avoid asking the colleague for help but there are things I simply need to ask him.
Also, sometimes it's simply difficult to catch him as we both have plenty of calls every day and the problems I deal with are normally urgent - I can't wait till the next weekly...
That's why I started to ask these questions in writing, giving our team lead in cc. This shouldn't be shocking also because the team lead tends to control very strongly what this colleague is doing, giving him advice, prioritising his tasks, etc. There have also been plenty of cases that the team lead actually overruled the colleague's decision.
Also, I want to have certain things in writing. For example that I requested some information - because without having it I'm stuck, I can't move forward with my project.
Our team lead now told me I am being aggressive and uncooperative. And that he expects me to talk to the colleague and not write emails which sound like escalations.
I'm at my wits' end.
What strategy could I use to ensure this colleague provides more useful assistance?
[EDIT] Of course I explained my motives and asked my team lead what I should do in this situation! He just repeats like a mantra that I should talk to the colleague.