If you feel concerned about communicating with more people at the same time, it is good to know that online dating etiquette considers it acceptable. There is no harm in writing emails back and corresponding with people who contact you. Statistically speaking, one in four or five emails gets an answer. Which means that the system does not follow a single thread as in 'you write to someone and wait for him/her to get back to you'. The rule is valid vice versa too; you don't contradict the online dating etiquette if you ignore some messages.
It is perfectly reasonable to ignore an email if you consider that the sender is not right for you.Don't compare the online dating etiquette with real life situations because the instances are different. How could you write back to a person and call him/her a bad match? A different issue is when you break up through emails.
If you have met online and then went on a real date, things can be more complicated. You can just send that person an email and tell him/her that you would not like to continue seeing each other. However, you would break the online dating etiquette if you met online but went out a couple of times. After several dates, you probably owe the other an explanation. Do it elegantly and in as friendly terms as possible. Plus, even when you date someone, you can still write to other people. That is considered acceptable.
It is totally against online dating etiquette to keep your profile up when seriously communicating with someone. When you commit seriously to an online relationship it means that at a certain point you will start seeing each other. You can still continue your online membership and keep your profile, but make sure the profile is no longer active. If you don't follow this very basic guideline you could very well spoil your chance of meeting someone who loves you.
Most of the rules in the online dating email etiquette refer to communication. Dishonesty, profanity and rudeness are totally unacceptable, yet they remain the main downside of dating services. Well moderated sites are less exposed to rudeness but every online dating web site is exposed to dishonest people.