The email signature can be a powerful marketing tool — but it can quickly become an irritating vehicle of self-promotion.

When to Use Your Email Signature for More Than a Sign-Off

This story appears in the March 2018 issue of Entrepreneur. Subscribe »

Two years ago, Alaia Williams used a run-of-the-mill email signature: title, company, phone number. But as an online business strategist, she wondered if she was overlooking an obvious opportunity. So she started adding to her signature, piece by piece. She placed social media icons to link to her Facebook, Twitter and LinkedIn accounts. She added a sign-up for her mailing list. She even threw in a head shot and info on her product line.

The results? Her followers and opt-in rates immediately increased. “I’m getting inquiries and referrals from people who don’t even know me well,” she says.

Williams’ instinct was spot-on, it turns out. Email signatures are no longer just an afterthought; they’re a valuable marketing opportunity. That’s because they typically come from a trusted source (or at least a professional acquaintance), and because getting a work email is a fundamentally different experience than, say, watching TV or scrolling through Twitter.

“When we read emails, we’re in work mode,” says Richard Hanna, a marketing professor at Babson College and the lead author of Email Marketing in a Digital World. “We’re actively engaged in reading material related to what we’re doing, and we pay more attention to the signature.”

Related: Want to Create the Holy Grail of Mailing Lists? Follow These 5 Tips.

Email marketing firms like Hubspot, Sigstr and WiseStamp offer…