Deliverability tips to avoid the spam folder this holiday season

Every holiday season is a vital time for email deliverability. Get Mailjet's tips on avoiding the spam folder and getting under the email tree. Read more...

Hermes riding the sleigh

The holiday season is almost upon us, which means marketers (especially those in retail) will begin to increase their sending frequencies, and will also widen their nets to reach out to as many contacts as possible. At Mailjet, we’re expecting to see very high volumes coming from our senders and the risk to deliverability increases as a result of emails being sent to older and more inactive or disengaged contacts.

Both of these actions can lead to poor deliverability if not done with care.

Of course, this isn’t something that only Mailjet faces, as anyone in the email industry – email marketers, other email service providers, and deliverability services – can all attest to. So, in an effort to ensure the email industry is best prepared for the holiday season, we thought we’d share some tips on how we are approaching it this year.

Plan ahead for the holiday season

In short, just like preparing for your holiday parties and gift exchanges, the best piece of advice we can give to you is… plan ahead!

We understand that most retailers make the bulk of their revenue during Q4, so the stakes are high. But at ISPs like Gmail, Outlook, and Yahoo!, the email volume level is also incredibly high, and they can tend to take longer to mitigate deliverability issues during this period of high email activity.

While we cannot magically fix all problems, preventing a deliverability issue through responsible sending and a well-planned holiday strategy is how we can help ensure success this season.

Here are some key dates with huge sending volumes to keep in mind this holiday season:

  • Nov 20 – 25: Week leading up to Black Friday, to advertise upcoming sales

  • Nov 26: Black Friday (historically the biggest email day of the year)

  • Nov 27: Small Business Saturday

  • Nov 29: Cyber Monday

  • Dec 6 – 24: Weeks leading up to Christmas, to advertise holiday sales & wish their customers a happy holiday season


At Mailjet, we often see increase in email volume of nearly 60% on Black Friday, and 17% on Cyber Monday. Considering that sending high email volumes during the holiday season is a global trend, it’s important to remember that ISPs have to handle this additional load of emails from everyone around the world.

This can lead to delays in email delivery and sometimes even temporary deferrals for good senders since the ISPs servers are overloaded with messages. Holiday sending activities are also known to lead to stricter and more aggressive ISP spam filtering (making it harder to hit the inbox), and longer turnaround times on responses from ISP Support teams when email service providers like Mailjet reach out to them to resolve deliverability issues.

The key to strong deliverability during the holidays is to plan ahead and have a well-thought-out approach.

The most common mistakes we tend to see during the holidays

Increasing sent volume “overnight”

An example of this would be going from a smaller and more targeted list of “active recipients” (those who have signed up, opened, or clicked on an email within the past 3-6 months), to contacting “everyone in their contact list” without ramping up to the larger volume slowly, over the course of several sends.

ISPs will perceive any large increases in volume from one campaign to the next as “spikes“. These are viewed very suspiciously by the ISPs, since they mimic spammer behavior, and can lead to spam folder placement and blocks.

To play it safe, any increase in volume from one day to the next should not be more than roughly 25% larger than the maximum daily volume you’ve sent within the past two weeks. For example, if you typically send to 100,000 recipients, you should target no more than 125,000 in the next campaign, then 156,000, and so on). Given this compounding growth, you should get to your necessary list size relatively quickly.

Senders with great data quality and reputation can sometimes get away with much larger increases in volume, but this is not recommended – especially during the holidays.

This recommendation is especially important for senders on dedicated IPs, but it is also important for shared pool senders because some ISPs (like Gmail) track reputation at the sender address and domain level, so spikes in volume from one particular domain can also be viewed as suspicious.

Want to know more about how to warm up your IP address to ensure good email deliverability? Check out this Email Is Not Dead podcast episode from our friends at Mailgun.

Sending to inactive or disengaged contacts who haven’t been targeted in a long time

Some examples of this include “addresses which have not been emailed to since last holiday season” and “anyone who has not been sent an email in more than 3-6 months”.

Sending to inactive or disengaged contacts can lead to high hard bounce rates and spam trap hits if the addresses being contacted no longer exist. Both of these can cause deliverability issues.

We can also expect to see low user engagement (i.e. opens/clicks) as well as higher-than-normal user complaints and unsubscribes if someone hasn’t been contacted in such a long time that they “forgot” they signed up. These also lead to deliverability issues, particularly high complaints.

It’s ok to reach back to your more inactive or disengaged segments but do so carefully. It’s important to remember that you will make most of your money (and receive the highest engagement) from your active recipients. The only way to optimize your ROI on your active subscribers is by ensuring 100% of your email is going to the inbox. Sending to inactive or disengaged contacts can compromise this.

We recommend keeping the new “inactive/disengaged” segment to no more than 10% of the daily volume you plan to send as a start. If the test goes well, then you can try increasing it the next time you send. But do it slowly!

If you see signs of any of the problems mentioned above, you can pause and re-assess if it’s still worth targeting inactive or disengaged contacts (knowing it will lead to poor inbox delivery for both inactives AND actives).

Increasing the frequency of sending to the point where users are overwhelmed by “inbox noise”

This is another very common example around the holiday season. An example would be a company that normally sends newsletters about sales once per week, and is now sending 3x per week (or daily).

If recipients are not used to this high frequency and become overwhelmed or annoyed by it, or simply don’t find the content useful at that frequency, it can lead to higher complaint and unsubscribe rates, as well as lower open and click rates. All of these reactions are viewed negatively by ISPs, leading to junk foldering and blocks.

It’s OK to increase frequency, but you need to provide valuable content that is worth the recipient’s time, attention, and inbox placement.

Also, remember that it is not only you who is sending more emails during the holidays… it’s basically everyone on the internet! Which means you are fighting for recipient attention. More email in a recipient’s inbox (from you, and the rest of the internet) means less chance for one particular email to be read. As a result, you might see slightly lower open rates due to seasonality.

Last-minute deliverability checks before the holiday season

Now that we’ve seen the most common mistakes to avoid during the holiday season, here are a few more tips to improve two critical elements for your email deliverability: your sender reputation and the content of your emails.

Sender reputation

ISPs take into account different factors to determine your sender reputation. Authentication is only one of these factors, but it is the first step to success. There are several authentication protocols that you must use to show ISPs that you are a good sender. And trust us, you want to be considered a good sender.

  • SPF: An SPF record on the DNS server (a service whose main function is to translate a domain name into an IP address) allows domain name owners to look after their reputation by deciding who has the right to send emails on their behalf. Any person who is not on the list of authorized addresses is considered an imposter.

  • DKIM: DKIM is a standard used by ISPs to verify that no phishing acts have been committed during the email routine. It adds a unique signature to the email you send. The receiving server can check the domain signature to confirm the origin of the message and to ensure that its content has not been manipulated along the way.

  • DMARC: DMARC is an additional protection measure against domain name theft. If SPF and DKIM systems fail, the DMARC standard tells the recipient’s receiving server whether the message should be rejected or considered spam.


Email content

In terms of content, there are several elements that trigger ISPs’ alarms. Here are the main tips to follow when designing your holiday emailing campaigns so ISPs don’t think you’re a spammer:

  • Keep your subject line between 35 to 50 characters long.

  • Do not use ALL CAPITALIZED WORDS in your subject line or body.

  • Avoid using spammy-seeming words (‘Free’, ‘Sale’, ‘Cash’, ‘Limited Time Offer’, etc).

  • Send content that your subscribers have signed up for and are expecting.

  • Use a text-to-image ratio of approximately 60% text and 40% image.

  • Include an unsubscribe link in each of your marketing messages.

More resources to prepare your holiday campaigns

It’s time to start putting together amazing holiday email marketing campaigns that will help you to embrace the holiday feeling to build your brand and drive sales.

We’ve combined all our holiday resources in one to create your one-stop shop to win the battle of the inbox this season. In our Ultimate Guide To Holiday Emailing, you will learn how to create amazing content for your campaigns, find great design tips from some of our friends in the industry, and get inspiration from great email examples by top brands. Put that holiday cheer to good use!


Send your holiday email campaigns with Mailjet

Create and send the best holiday email campaigns with Mailjet. Use one of our predefined holiday email templates or design your own with our drag-and-drop editor and send them straight to the inbox.


This blog post is an updated version of the post “Deliverability Mistakes to Avoid During the Holiday Season”, published on the Mailjet blog on November 7, 2019 by Lauren Meyer.

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