Email marketing continues to dominate how businesses connect with their customers. Nearly 105 billion emails are sent each day; this number is expected to reach 246 billion before 2020. With potential customers facing this inbox deluge, crafting an email that stands out becomes a challenge.

According to Mastercard SpendingPulse, the 2017 online holiday retail sales experienced 18.1 percent year-over-year growth, outpacing retail sales growth overall. Cyber Monday 2017 was the biggest e-commerce day in U.S. history.

Here’s a look at several emails online retailers delivered during last year’s holiday season.