Other people have three ways of contacting you on the forum, all available via little buttons next to each and every post.
Respond publicly. Not an issue.
Respond via PM (private message) which requires you to be logged in to notice it. You may or may not get an email depending on your profile settings. If you do have PM's they'll be shown with a bright red number at the top bar.
Respond via email which requires you have a functional email address. I know that some prefer to use throw-away addresses for registering. I'm okay with that, but it also means that people trying to talk to you might be sending their comms into a black hole.
IOW, when responding privately to other forumites please consider that they may not receive your comms due to unintended side-effects of their online behavior.
For example: I currently have 9 outbound PMs sitting, and some have been sitting for a while.