Sending emails is an integral part of selling in today's world. But at a time when prospects are receiving hundreds of emails every single day, it is easy for yours to get lost in the crowd.

What's even more frustrating is since this technique is relatively new in the realm of sales prospecting, up until now there has been little data to show which prospecting email techniques actually work. But thanks to data pulled from HubSpot Signals email tracking software, we can get a rare glimpse into what actually works most effectively for getting our emails read.

HubSpot has produced a new report that contains information from 6.4 million one-to-one emails sent from Signals users. Pulling from this user pool allowed HubSpot to identify which individually sent emails were actually being opened and which were being ignored. Here are five tips based on this data that will help you send emails that lead to closed sales.

1. Send emails during off-peak hours

Many salespeople send the majority of their prospecting emails during the middle of the week to give their prospects a break from emails on the weekend. However, open rates for emails sent on Saturday and Sunday are actually higher than those for emails sent during the week.

An email sent on Tuesday has a 58 percent chance of being opened, whereas an email sent on Saturday has a 65 percent chance of being opened. This means you might want to rethink when you are sending your prospecting emails. Try sending them out on the weekends, and see if you find similar increases in your open rates.

HubSpot

2. Choose your words wisely

Typically, the first part of an email you will read is the subject. That's why what goes into your prospecting email's subject will often determine whether the rest of the message ever gets read.

HubSpot found that emails with the words "you," "quick," "meeting," and "fw:" were less likely to be opened by a prospect. On the other hand, emails with the words "free" and "tomorrow" or emails with no subject whatsoever had higher open rates. So test crafting your emails with and without some of these words in order to see which emails have higher open rates.

3. Show you've done your homework

Think about your own process of sorting through emails. After you've looked at the subject of an email, the first sentence of the message will be critical in your decision to continue reading.

This hook is even more important when you consider the prevalence of smartphones today: A phone will often display the subject of an email and a preview that includes the first few words of the message.

Because of this feature, your first sentence must be highly personalized to show that you know something about your prospect and her company. If the email appears boilerplate, the prospect will immediately delete it.

4. Engage the prospect with an easy question

Oftentimes, we forget what the purpose of a prospecting email is in the first place. The goal of an email is not to close a sale, but rather to engage the prospect in a conversation that can lead to a phone conversation or face-to-face meeting.

Therefore, be sure that your prospecting emails inspire prospects to respond to you. End every email with an easy-to-answer question. Try something simple and quick like:

• Is this a challenge you face in your business?
• What's the best address to send this report to?
• What's your biggest marketing-related priority right now?

By closing your emails with a question, prospects will be more likely to respond because you've (1) engaged them directly and (2) removed the guesswork surrounding what kind of information you need from them to move forward.

5. Use email tracking software to collect data

Until now, salespeople have been left in the dark as to when a prospect actually opens their email. However, thanks to some pretty amazing technological breakthroughs from products, such as HubSpot Signals and Yesware, we can now know exactly when a prospect opens our personal emails.

Since both companies offer free trials for these great plugins, be sure to download one and watch your world of email prospecting change forever. Also, now that you know when a prospect has opened your email, you can follow up with a call and increase the likelihood of getting through.

And now that you have the ability to track which emails get opened, test different combinations of subject lines and first sentences to see which trigger prospects to click through most often.

By applying these five tips to your prospecting emails, you will see a significant increase in open rates, responses and, most importantly, closed sales. Which of these tips did you find most useful? Please share below in the comments.