The majority of emails, some 90-99 percent, sent through Yahoo's email system are spam, according to Jeff Bonforte, senior vice president of communications products at Yahoo Mail. In an interview with Tech Insider, Bonforte revealed that about 30 billion emails come through Yahoo's email system, and only a handful of those are actually delivered, the rest are rejected as spam. In fact, the company only delivers about 5 billion per weekday, and 2.5 billion on weekends.

While marketers sent more than 30,000 Halloween-related email campaigns during the month of October, their efforts were not that successful. Only 6 percent of Halloween-related email marketing messages had a more than 20 percent open rate, according to an analysis from eDataSource. Still, some marketers did manage to get through. Amazon, for example, earned a 42 percent open rate with the email subject line: "Halloween Costumes, Candy +More."

Most people in the U.S. use email and text for all kinds of business, but they can't use it to communicate with doctors. According to a new report from Nielsen, whichpolled more than 5,000 Americans ages 18-65, only 15 percent of those surveyed use email to communicate with their provider. The research found that this might not change any time soon. Only 11 percent of the 626 doctors interviewed for the survey recommend email reminders.

Marketing services firms Boomtrain and Marketo have integrated their platforms to allow companies to deliver more personalized content online. Marketo captures website and email data and now Boomtrain can use attributes from this data to predict the best piece of content to deliver to individual customers. Brands that use both platforms can push this targeted content via email or through on-site campaigns.

DonorsChoose.org, a nonprofit that helps public school teachers by raising funds for supplies in their classroom, raised $75 million in 2015. According to Abby Feuer, vice president of marketing for DonorsChoose.org, who spoke recently at a panel at the Fast Casual Executive Summit in Miami, 20 percent of that revenue was raised via email. The organization has more than 1.8 million supporters.

Small business Southeastern Underdeck Systems sent out an email last year on Cyber Monday just because. The email, powered by Constant Contact, offered 15% off for one day only for customers who booked an unreduced installation. The company's owner Heath Bowman was surprised that the email led to 27 jobs booked, and $67,000 in sales. This was the most jobs he had ever sold in a single day.

Anonymous has threatened to share the names of 1,000 Ku Klux Klan members in order to mark the one-year anniversary of "Operation KKK," the group's effort to shut down the racist organization's web presence. The hackers have already posted 23 email addresses and 57 phone numbers of these members online.

Google wants to make responding to emails easier. The company is rolling out a new feature for its Inbox app called Smart Reply that will analyze the contents of an email and suggest three possible ways to respond. The feature works like autocomplete, but for phrases and short sentences rather than words.

While consumers are using their mobile devices to do a number of activity, email remains of the most valuable ways to reach consumers on smartphones. According to Pew Research, reading and writing email is the third most popular activity after text messaging and surfing the web. In addition, various studies show that more than half of email opens take place on a mobile device, suggesting that email is still a valuable medium to market on mobile devices.

Marketing services firm Zeta Interactive has closed the acquisition of the CRM division of eBay Enterprise. According to TechCrunch, Zeta Interactive paid between $80 million to $90 million in cash and stock for eBay's CRM unit. eBay Enterprise recently sold its Magento platform to a consortium of private equity firms led by Sterling Capital and Permira.