Whether they're selling to consumers or other companies, many small businesses still use email as a primary way to reach out to prospective customers. But messages often get lost in a bulging inbox and then deleted into oblivion.

Business owners who have been successful with email marketing say a subject line that stands out will help an email be opened, and a message that's to the point and interesting is more likely to get a prospect to respond.

Make a reader curious is the advice from business coach Jack Petry. He uses subject lines that make a potential client wonder, what is this about? For example: "Why Being Smart Sabotages Your Business" or "My Mom Thought I Was Crazy."

This approach can work no matter who the target customer is, but it can be particularly helpful for a small retailer competing with big online merchants, says Petry, who's based in Simsbury, Connecticut.

"Gap and Abercrombie & Fitch don't need to be creative or innovative with their emails, he says. "For a small business, it's a great opportunity to differentiate yourself."

Subject lines in emails to consumers, as well as the body of the message, should also have their first name, says Jeff Smith, owner of Castaline Insurance Agency in Laguna Beach, California. Software programs make that possible even when sending out a large number of emails.

Subject lines should be short, especially because so many people read their email on phones or tablets, says Paige Arnof-Fenn, owner of Mavens & Moguls, a marketing firm based in Cambridge, Massachusetts. She suggests owners trying to sell to other businesses find a way to personalize the subject line: "XYZ suggested we connect" or "Great talk at the conference this week!"

Similarly, the body of an email to a business owner needs to show that the sender did some homework about the prospect and can explain why and how they could benefit from the product or service for sale.

Arnof-Fenn doesn't always make a sales pitch in an email to another owner. Instead, she might start a conversation, a step toward building a relationship that perhaps will ultimately lead to a contract. Her attitude is, "let's just get to know each other, and if in six months to a year you need help, we already know each other."

No matter whom an owner is targeting, in writing an email, less is more, Petry says. He learned that lesson the hard way with emails that fell flat.

"I would write long emails and I would wonder, 'why am I not getting results?'" he says.

Learning how to write good emails is a process. Petry learned from business owners who were his mentors.

"Keep it conversational, like you're having a conversation with a friend, an equal peer, someone you care about," he says. And, keep it relatively short -- between 300 and 500 words. "Keep it dialed in and tight -- that will allow you to get your message across," Petry says.

Owners can also learn by reviewing the emails they get in their own inbox, and analyzing which ones work, and which ones don't. Many owners do tests, sending one email to half the prospects or customers in their database, and a different one to the other half. The response rates can show what's working in their emails, and what isn't.

After sending an email, owners should follow up, Smith says. If he has a consumer's phone number as well as their email address, he'll send an email first and soon after, send a text.

Many owners send follow-up emails. But they should do it sparingly -- bombarding potential customers will just mean the emails will end up in the trash folder.

--The Associated Press