If you’re prospecting via email and not very concerned about your subject line, you are making a big mistake. It’s the single biggest determinant of whether or not the recipient will decide to open your email.

A lot of people don’t even think about email subject lines. They write something such as “Company overview” or “Update on what’s happening with our company.” And of course, the person who gets this in her email box will think “Why do I care about that?” If you have anything about your company in the subject line, I promise you your email will be deleted — unopened.

The second type of subject line that will get your email deleted is anything that’s sales-y. Things such as special promotions, 50 percent-off sales or new product announcements will get deleted quickly, too.

So, what works? How can you craft a subject line that will get your prospects to open your email? If you have a referral, you should automatically put that in your email subject line. “Bob Smith suggested I get in touch with you.” This always gets people to open a message.

The second thing you can do is reference something that is important to the company. You solve business issues. You help people with projects that are important to them. Put something in the subject line that would be relevant to your recipient.

For example, I might use something such as “Quick question regarding new-client acquisition.” Or, I might mention something about new product launches or how the recipient’s competitors have increased sales of a new product. Mentioning competitors is definitely something that will pique your recipient’s curiosity.

You need to think about how your message would be interesting from your prospect’s point of view. Put that in the subject line. Make it about them; that’s all they care about. They don’t care about your company or anything you have to say about yourself.

If you can do that, you will have bought yourself a little bit of time, a little “in.” Now your prospect is likely to read the first couple of sentences of your message. And here, you will have another chance to capture his attention and encourage him to read further.

The subject line is the most important part of any email. Spend time crafting a good one — it’s that important.

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Jill Konrath is the author of SNAP Selling and Selling to Big Companies. If you’re struggling to set up meetings, click here to get a free Prospecting Tool Kit.