Electronic Work Communications vs. Off Hours Communications?

im and unhappily married man and i electronically communicate constantly at work with a divorced femail co-worker. but it hasnt gone farther than that. i try to electronically communicate with her during off-work hours. but she never responds off hours, but she's getting the msg off hours because she sometimes references the msg in person when we see each other again at work. she only responds during work. are electronic communications during work seen as friendly? but are off hours electronic communications between co-workers seen as a major step toward a relationship? it's like co workers are supposed to communicate during work. but why would they communicate outside of work, if nothing was going?