With all due respect to apps that are trying to replace email, email is not going anywhere. Having said that, people are getting more and more emails and it's difficult to stand out in their inbox, which results in their not replying to you.
There are some things you can do to increase your chances of getting a response.
Here are five:
1. The subject is not what you think it is.
If I asked you what the point of an email subject is, what would you say? If you're reading this on Inc.com, chances are you know a little bit about business. But when I ask people that question, many answer that a subject is intended to summarize the email. That is ridiculous.
If you sum up the email in your subject, I have zero incentive to open it. The subject is there to tease the recipient and hopefully get them to open your email.
In that way, a subject is similar to a tagline. "Just do it" doesn't tell me what Nike does, it just encourages me to say, "Tell me more." That is the goal of a subject; to make me say "Tell me more," which results in my opening your email.
2. Check your fonts and formatting.
This is a huge pet peeve of mine. If you can't be bothered to check that your fonts are all the same and that your formatting is OK, I can't be bothered to reply to your email.
Often, people will use an email template and simply paste the name of the person into the template. That results in the name and the rest of the email looking different and inconsistent.
A good way to ensure that all your fonts are the same is to copy all the text in the email and paste it in another app like notes or Twitter (don't hit Tweet!) and then copy-paste it into the email. The app often gets rid of the inconsistent fonts.
3. Choose the time you send it very carefully.
If you send me an email at 4 a.m. and I wake up to my normal inbox full of emails, the chances of my responding quickly, or even at all, decrease.
This is a symptom of a broader issue. When communicating, don't think of your needs, but rather of the needs of the recipient.
It might be 7 o'clock for you, but the person you're sending the email to is another time zone and it's 4 in the morning for them.
4. State your ask from the get-go.
Before you jump into your lengthy email (don't send lengthy emails), state clearly what the topic of the email is--what you're asking for--from the get-go.
For example, before you start pitching your startup, begin the email with "Hey, Hillel, I wanted to ask you for help with marketing/introductions to investors/help getting press."
By stating your ask in the beginning, you accomplish two things. The first is that the rest of the email is easier to understand now that the recipient has context. The second is that it saves the other person time if they can't help you with what you're asking.
There is no reason that person should read your long emails only to discover at the end that the whole email is totally irrelevant. Be mindful of peoples' time.
5. End the email in a way that encourages a reply.
Don't end the email in an open-ended way. End it in a way that gives the recipient an easy way to reply.
So, for example, you can end the email with "So what do you say? May I intro you?" or "See below. Is this a relevant initiative for you?" Or even "Does that make sense to you?"
Give the person an easy way to reply without writing a mile long email back.
All of these tips can be summed up with one principle, be considerate of others when communicating.