How many times have you sent email and never heard a reply? If the person at the other end is ducking you, there's nothing I can do. Sometimes, though, it's just a case of too many emails and yours getting deleted.
There are a few things you can do to reduce the chances of your message getting lost.
Step 1: Is it getting through? Try sending to someone outside of your company to ensure that there aren't technological problems blocking your messages.
Step 2: Is email the right medium? If it's a really short tidbit, would IM or a text message be more appropriate? If it's really long, would the phone or a face-to-face conversation be better?
Up to 85 per cent of human communication isn't what we say, but in how we say it. "That's so awful" said with an expression of concern is supportive and caring. The same thing said while you roll your eyes is sarcastic and cutting. I'm not saying you should never be sarcastic and cutting, just that you should only do it when you mean to.
With email, you lose most of the message. That's why mis-communications are so easy by email. You should never use email to talk about emotionally-charged topics. It will only serve to add fuel to the fire.
Step 3: Use CC carefully. Are you including people who don't need to be included? I worked in one setting where someone was sending enough mails to firstname.lastname@example.org that I eventually set up a rule that blocked all emails from her.
Step 4: Use a clear but descriptive subject. I should know from your subject what you want to talk with me about. Extra points for clarifying what you want me to do about it. "Need quote on new laptop" is a lot more useful than "Got a minute?"
Step 4: In the body of the email you want to strike balance between being too curt and too chatty. A pleasant greeting is fine, but don't go into a long-winded description of what you did this weekend. Email is best used for a communication of facts, not chit-chat.
Step 5: Proof-read before you send. It only takes a few seconds and can avoid a frustrated, "Huh??? What is s/he talking about?" at the other end.
Paying a little attention to what you send, how you send it and who you send it to can do wonders for making better use of email as a tool.