If you haven’t written a cover letter in 10 years, and don’t know how dramatically they’ve changed, you might as well pick up a stone tablet to compose your next one. In the age of applicant tracking software and emailed job applications, everything about cover letters is different—from tone and content, to purpose and relevance.

The rise of job boards and online application systems has made cover letters an unreliable self-marketing tool—at least online. If the computer tosses out your resume, your uploaded letter gets trashed too. Even if your resume makes it through the screening, the person reading it may not bother with the cover letter. It’s a secondary document at this point, not the grabber it’s supposed to be. “With online systems, cover letters sometimes get read, and sometimes not,” says Lindsay Barbarino, Team Lead of Resume Services for RiseSmart, an outplacement service in San Jose, California. “But they are pretty powerful in the cases they are read. They can tip the scales.”

While uploaded cover letters are often overlooked, ones sent as email are almost always read. “Body copy is the new cover letter; that’s your first impression,” says Chris Lawson, chief executive of Eli Daniel Group, a boutique recruitment firm in Allen, Texas. If you’re able to apply directly to a hiring manager via email, your cover letter will be your greatest ally in landing you an interview.

Here are five rules for crafting a killer cover letter—and getting it read.

Forget about you; learn about them. Your resume lists your experience, accomplishments and skills; your cover letter should show how they are relevant to a particular job, and to the company’s goals. Before you write a word, research the company and the industry so you can make informed references in your letter. “Look at the company’s website—what are they actually doing in the marketplace? Get to know who their competition is,” suggests Lakewood, Colorado career coach Donna Shannon, author of Get a Job Without Going Crazy: A Practical Guide to Your Employment Search. Shannon recommends looking at ZoomInfo and Manta for company information, Glassdoor for insight into hiring trends, and LinkedIn for information on the hiring manager and other company employees.