Firstly, you would have to clarify who you are writing to and why? The corresponding author is there mainly for anyone who reads the article and has a question or query about it i.e. can you share aspects of the article i.e. further data, permissions etc. That you are not the corresponding author should not stop you contacting people in relation to your work - whether you are first author or not. You may just want to ask the other author's advice first - top save any issues arising.
In the previous case, I was the second author in one journal. I realise that the job of the other authors, except for the first author and the corresponding author, is to accept the decision. If the other authors have any comments regarding the research contribution, they can consult with the first and corresponding authors.