It's party season for the media and marketing community in Manhattan, home to weeks of lavish NewFronts and upfront events where TV networks, digital startups and old-school publishers pitch their shows and digital-video series to advertisers.

But at the same time a far less flashy medium is capturing the attention of media execs: email. An email newsletter called TheSkimm, for example, is reaching young women by delivering the day's news in a breezy conversational way, like your friend telling you what's happening in the world.

"They're killing it among that demo," one high-ranking digital-media executive told me recently.

Though TheSkimm began three years ago, it's been on a tear in the wake of a fresh $6 million investment round in December from backers including Greycroft Partners and RRE Ventures. The newsletter now reports 1.5 million active users per month and a 45% open rate. It has big brands such as the NBA, HBO and Netflix paying to run native ads, and counts Oprah Winfrey, Reese Witherspoon and Tina Brown among its celebrity fans.

Founders Danielle Weisberg and Carly Zakin, both not quite 30, make the very bold claim that they're building a media brand to chip away at the viewership of TV morning shows.

"We're deconstructing morning-show behavior," Ms. Weisberg said. "Skimm readers are rolling over, grabbing their phones and getting their news."

And as for advertisers, they're trying to work with brands that "represent the Skimm life," according to Ms. Zakin. "We've literally gotten thank you notes from users to say thank you for working with a brand in this way," she said.

There's no sales staff, however. Mses. Zakin and Weisberg say they're heavily involved in running "partnerships" with brands -- their term for advertising. "We're not hiring traditional sales people because we're not doing traditional ad sales," Ms. Weisberg added.

Neha Gandhi, vice president of editorial strategy at Refinery29, described Mses. Weisberg and Zakin as "smart, driven women who have turned their newsroom backgrounds" -- they're former NBC News producers -- "into a daily product for millennial women that's incredibly accessible, digestible, and useful."

"In a way, they are going back to what Daily Candy used to do back in the day -- or what Goop did up until recently," she added. "Giving it all away in the email and making it super-easy to consume. And when you wake up in the morning and just want to, well, skim, not having to put up with that extra click is pretty compelling."

TheSkimm is part of the recent explosion of email newsletters that are fighting for your attention and, in many cases, brands' ad budgets. Another that stands out belongs to The Pool, a website whose newsletter claims a 60% click-through rate. Old-media brands are giving email a second look, too. Executives at Time Inc., the nation's largest magazine publisher, have discussed subscription models for emails from Fortune, people there tell me.

Advertisers, meanwhile, are expected to spend $270 million putting ads in email this year, according to eMarketer. That could grow to $340 million by 2019.

"We've seen advertisers' budgets leak over into email from display," said Todd Garland, founder of BuySellAds, an ad-tech company that puts ads in emails and websites. "We don't fight fraud in email as much as we do in display. We don't fight viewability issues."

For TheSkimm's founders, however, email is only the beginning. "It's the anchor," said Ms. Zakin. "We'll be taking our voice and community to a different platform."

They declined to elaborate on what that platform might be, but people with knowledge of TheSkimm's business say video is likely its next frontier.