The holidays are a distant memory for some—for others they’re a big looming target on the horizon 10 months from now. Whatever perspective you take, the truth of the matter is that every iteration of the holiday bonanza is an opportunity to experiment and learn. And yes, capitalize on the growing opportunity to engage and convert new and existing customers.

The Big Picture

I’ve said it before and I’ll say it again: email is a highly instrumented channel that allows senders to benchmark their performance across numerous data points and vectors. Twilio SendGrid processed over 4.2 billion emails on Black Friday in 2019 and over 4.3 billion emails on Cyber Monday. The trend chart below shows you the growth of our platform from SendGrid’s inception and, although it’s not causal, the growth of the holiday shopping event which reaches new highs with every trip around the sun.

Setting the stage with our holiday weekend volume helps contextualize the next set of metrics. Our analysis is based on a massive data set that continues to grow and expand every year. Here’s another look at just the holiday week over the past four years:

There is a sustained and noticeable volume increase across the entire sending week in addition to Friday and Monday.

Mobile Clicks

We’ve known for some time that the bulk of email is opened on mobile devices. The mobile tipping point came and went some years ago—web analytics companies routinely report on how mobile sales surge year over year. Instead of looking at something we already know, we decided to look at what happened when recipients opened email on mobile devices: the all important click.

65% of all click activity during the week of Black Friday and Cyber Monday happened on a mobile device! Not only are people actively opening emails on mobile devices, they’re vigorously clicking links in those emails.

Stating the Obvious

Every year we try and understand if including a mention of the holiday in the subject line has a positive or negative effect on engagement with the email. As in previous years, not mentioning the holiday has a higher engagement rate than a mention of the obvious: it’s a holiday. Similar to previous years, Black Friday engagement was slightly higher than Cyber Monday’s engagement for emails that mentioned the holiday. The takeaway here is that recipients know what’s happening. Senders should focus more on delivering value with an email and less attached to using subject lines like calendar reminders.

Urgency in Subject Lines

Similar to reminding recipients of the holiday, urgency can have a negative effect on the engagement of emails. We looked at urgency in three different contexts: between Black Friday and Cyber Monday, the week leading up Christmas and between the holidays. If you wanted to play it safe you’d avoid making your subject lines too urgent. However, the mention of “tomorrow” in emails around Black Friday and Cyber Monday did appear to have a higher engagement rate than “now,” “soon,” or “today.” Let’s assume that our recipients are aware of the date and the holiday (that makes our job simpler). Instead, remind them about the brand, our products and what they stand to gain or lose, rather than the timeframe.

Subject Line Length

There have been volumes of guidance written on how to craft good subject lines. Entire keynotes at marketing conferences have been dedicated to hacking subject lines live and providing psychological guidance on how to motivate recipients through cleverly wordsmithed subject lines. Based on our analysis, 34 characters is the most popular (widely used) subject line length.

To Discount or Not to Discount

If the length of subject lines dominate much of the popular thought in how to craft a good and effective subject line then the discount might be the next most important, and hotly debated, topic to consider.  Our analysis showed that the days between Black Friday and Cyber Monday had the highest percentage of emails with discounts in the subject lines:

Including a discount during Christmas seems to be less prevalent, even more so than the days between holidays. However, where the rubber meets the road is the effectiveness of discounts in so far as engagement is concerned and here we see an inverse relationship. Emails with no discount in the subject line universally had a higher engagement rate than those that featured a discount:

When we looked specifically at the kinds of discount rates offered, we see that 50% and 20% are the most popular discount rates in subject lines:

However, when we examine engagement by discount rate we see that 20% and 50% were not necessarily the discounts with the highest engagement rate. Overall higher engagement rates had less engagement vs. a 60% rate that seemed to pique people’s interest.

Discounting is a complex question that requires an enormous amount of data well outside the realm of emails and subject lines. However, what we can say with confidence is that relying on discounts in the subject lines will not deliver the engagement lift marketers would like to think and hope it does. Marketers should focus on value, cleverness, understanding what the brand means to recipients, and differentiating their subject lines and emails from competitors.

!!! & 💙💙😀😀👍👍👌👌💥💥

As the heading here says, exclamation points and emojis are not to be overlooked when it comes to debating their merits in subject lines. However, the data, year over year, is clear:

Using a bunch of exclamation points in your subject lines doesn’t increase open rates. The same is true for emojis:

Both are similar to urgency or reminding people of the obvious: it’s a holiday. There is no doubt that some segment may respond well to clever uses of exclamation points and emojis, but this is one of those things that you should test specifically instead of throwing them to attempt to differentiate your emails in the inbox.


After reviewing billions of data points we continue to see similar themes play out year over year: recipients know what’s happening and engagement happens when senders truly understand what their recipients want and need during the holidays.

Reminding people of the time of year is a turnoff. Too much urgency also doesn’t have the desired effect, nor do !!!s or emojis. For all intents and purposes this is not what recipients respond to. These broad patterns though are not indicative of every segment and every kind of recipient.

Senders should test and segment their emails to achieve, as much as they can, personalization. Personalization is a loaded term as it tends to be more aspirational than anything. However, if it were possible, the perfect segment would be a segment of one: a single email purpose-built for a specific person. Short of that, senders should do their best to identify as many nuanced segments as possible and through testing determine the subject lines and discounts that speak to these segments.

The holidays for some are in the rear-view, for others they’re an active planning cycle that started on December 26th. Whatever your perspective, there are good, fresh learnings from the event that can help inform not only next year’s holiday bonanza but the many campaigns and communications that will fill the days between then and now. For more email engagement data, check out our Email Benchmark Engagement Study. Happy Sending!

Len Shneyder is a 15+ year email and digital messaging veteran and the VP of Industry Relations at Twilio SendGrid. Len serves as an evangelist and proponent of best practices and he drives thought leadership and data-driven insights on industry trends based on the massive volume of email SendGrid delivers on behalf of their customers. Len is a longtime member of M3AAWG (the Messaging, Malware, Mobile Anti-Abuse Working Group) and served on its board in addition to Co-Chairing the Program Committee. He’s also part of the MAC (Member Advisory Committee) of the EEC (Email Experience Council) where he serves as the organization's MAC Chair. The EEC is a professional trade organization focused on promoting email marketing best practices. The EEC is owned by the ANA (Association of National Advertisers), a nearly 100-year-old organization where he also sits on the Ethics Committee. In addition, Len has worked closely with the ESPC (Email Sender & Provider Coalition) on issues surrounding data privacy and email deliverability.