Here's the problem with written stuff - you either have to say it in a way that can not possible be misunderstood, or you will have to assume that the receiver will understand it the same was you intended.
Personally I wouldn't consider this to be negative if I saw it. However, if I didn't like the author of the e-mail, I could be possible blinded by that emotion, which could lead to thinking "hmmm, was he/she sarcastic? Maybe it's a hidden message meaning 'I don't want you to reply'?"
You can't express the intonation and gestures/facial expressions in the mail, so you can not be 100% sure how it will be interpreted.
Unfortunately, the alternative to this would be writing something like
"Although I sincerely hope that you will write a reply to me, it is not necessary. By this I do not mean that I don't want you to reply to my e-mail, but I rather want to express that I will accept any course of action you may take without being offended."
So I would not bother too much about it, and would just hope that the receiver will understand it properly.