Email deliverability do's & don'ts during the holidays

A marketer's guide to navigating the peak season email rush

Peak holiday sending season is just around the corner and you are most likely already making your preparations. If not, there’s still time to make sure your peak season sending is a success. Whether you are ready and raring to go or just now starting to prepare, this guide will make sure you are both set up for success and prepared to address any holiday surprises along the way by identifying the email marketing and email deliverability challenges you are facing, the risks that come with those challenges, and the tools you have available to address them.

The challenges of email deliverability during peak season

The massive increase in global email volumes during the holiday season puts stress on both mailbox providers and recipients.  In order to accommodate this extra volume of incoming messages and also protect their users from mail that looks like spam, mailbox providers become less trusting of messages in general and more reactive to signals of spam–i.e. spam complaints, delivery attempts to bad addresses or full inboxes, and sender volume increases that presents as atypical. 

The influx of messages from all manner of brands and senders can similarly tax the patience of recipients and lead to increased spam complaints. 

Whatever signals a particular mailbox provider is reacting to, the typical consequences are one of two outcomes: 

  • Suspicious mail is refused for delivery and is blocked or
  • Suspicious mail is quarantined to the spam folder or junk folder.

While neither outcome is good, and both mean your message didn’t get to the recipient, the good news is that negative email deliverability outcomes almost always have the same general causes: 

  1. Delivery of messages to people that report them as spam, 
  2. Delivery of messages to high volumes of recipients that are not positively engaging with your email, and/or 
  3. Delivery to addresses that otherwise indicate the sender is not adhering to permission-based email marketing best practices such as sunsetting old, unengaged addresses and only sending to directly opted-in recipients.

The three levers for email deliverability control

As you continue developing your holiday marketing strategy, building in mechanisms that help you control for those key causes of negative email deliverability outcomes will lower your stress, prevent disaster, and empower you to deliver successful holiday results. 

As a sender, there are essentially three general levers that you can ‘pull’ to prevent and repair deliverability problems:

Lever 1: Who you send to

Recipients mark messages as spam when they don’t feel like they’ve signed up for the messaging they are receiving from the sender they are hearing from. Sending relevant messages to recipients that have opted in directly to hear from your brand is the best way to limit spam complaints and ensure that your audience is engaged.

Lever 2: What you send

Messages that are relevant with clear calls to action and accessible, simple designs encourage positive engagement over time and helps to prevent spam complaints.

Lever 3: How often and for how long you send to recipients

A quick way to harm your sending reputation and your ability to get mail to the inbox is to send too much mail to recipients and/or too many messages to recipients who are not engaging with the mail. Make sure your sending frequency to individual recipients matches the freshness and relevance of your content. Also, limit sending to any addresses that have gone a long time without engaging. It is suggested to never send to an address that has gone more than a year without engaging positively with your email messages.

The remaining sections of this guide are designed to prepare and equip your email deliverability strategy for using the three deliverability levers to safely manage any anticipated sending period where volumes and/or results can be more volatile than normal. 

What to do before the holidays

First, take inventory of your current email program and evaluate your email deliverability health.

Look at your email deliverability stats over recent weeks and identify any mailbox providers or domains where your results are out of line compared to other providers. For apparent inboxing/spam filtering problems, reduce your sending volume to the impacted provider(s) by adjusting targeting so that only your most engaged recipients receive from you until you see over performance. If you see issues where mail is not being delivered, look into bounce reasons for context on why and how to mitigate the issue.

Evaluate your templates to make sure the HTML is as tidy as it can be, that the designs are accessible for all audiences, and that your links are secured with HTTPS. 

Avoid spiking your volume suddenly during the holiday season. Plan a few larger than normal sends prior to crunch time so that you never more than double your volume in a single day compared to your highest volume day in the last 30 days.

Next, create a sending calendar and outline goals for your campaigns. Build in breaks/off days where you are not sending anything. Things outside of your control can and do happen. Having off days allows you more flexibility to react to sending emergencies without overly endangering your reputation by sending too much mail.

Identify any relevant ‘deadline’ dates such as shipping deadlines and try to plan your content accordingly to avoid last minute “shipping deadline” campaign creation and sending. 

“Warm up” your audience by teasing or previewing what to expect from you during the holiday season. Even when your mail reaches the inbox, having recipients actively anticipate your messages helps keep them from getting lost in all the other messages. 

Define what success looks like and how you’ll measure conversions. It’s not sufficient to measure success by open and click rates because, as we know, those are not accurate indicators of marketing success. 

Measuring conversions or other first party data points and comparing the results across mailbox providers can provide extra insight into whether performance issues are problems with conversion or with email deliverability.

What to do during the sending frenzy

Continually optimize the things you can control.


While there can be a lot of pressure to drive the raw number of conversions upward by simply sending more emails, that practice also harms your ability to get future messages to the inbox as it increases the negative impact of sending to unengaged recipients.

If you must send to recipients who’ve gone a long time without either hearing from you or engaging with your messages, try to at least limit how often you target those recipients compared to your core, engaged audience.

It is suggested to never send to an address that hasn’t positively engaged with your email in over 12 months.


Use your data to send more compelling, personalized content and offers.

The more tailored your content is to your recipient’s interest, the more likely they are to convert and to create positive email deliverability signals.

Send timing and recipient frequency

Don’t send exactly on the hour. Schedule your campaigns to start sending at times that are not exactly on the hour or the half hour. It can help your messages avoid high traffic congestion at mailbox providers like Gmail and Yahoo to have your campaigns begin sending at a time such as 9:12am rather than at 9:00am.

Schedule sends strategically

For example, instead of simply scheduling your campaign to begin sending at 9:00am, you could try sending to your VIPs/most engaged recipients first at 8:43am, your somewhat engaged recipients at 9:07am, and then finally to your lesser engaged recipients at 9:30am.

This means those most likely to want and engage with your messages are more likely to get them quickly and to generate positive signals. Those positive signals will help the remaining messages deliver more successfully and will help to postpone the bulk of negative signals mailbox providers see until the end of your sending.

Keep track of recipient messaging frequency

Ensure recipients are not being over-messaged as this drives spam complaints.

Pro Tip: Sign your personal address up for your own marketing.

Don’t expect zero latency delivery

Craft CTAs that are not overly time-bound as the time it takes for a message to reach a recipient from the moment your campaign begins sending can vary based on many variables – the size of your campaign and audience, any dynamic content, your sending reputation at each mailbox provider, and even technical issues that can occur on the mailbox provider’s side.

Monitor Vital Signs


Hard Bounces

Elevated rates of hard bounces tend to point to problems with your list hygiene. Are you sending to a lot of old addresses? Could you have a signup form that is being attacked by bots? The main goal is to address the source of the bad addresses as these are often accompanied by other addresses that also cause problems like complaints.

Soft Bounces/Blocks

First, look at bounce reasons for clues as to why the messages are being rejected. While not all bounce reasons are easy to read or even helpful, it’s often the case that ones related to your sending reputation or behavior will have language referencing ‘blocked,’ ‘blocklisted’ or ‘blacklisted,’ ‘spam,’ ‘spam content,’ or ‘reputation.’

Oftentimes, if you need to contact a third party to resolve the blocking issue, there will be a link to instructions in the bounce reason. Each third party has its own process for ‘delisting’ a blocklisted or blacklisted IP or domain.

Increasingly, reputation-based blocks require a change in behavior on your part before delivery issues automatically resolve. Adjust who you are sending to so that you are not sending to addresses that are likely to complain or have not engaged with your mail in a long time. 

Low Open Rates

Seeing open rates significantly lower at some mailbox providers compared to others most often indicates increased filtering of messages to spam at the impacted providers. Target those mailbox providers with adjusted targeting that identifies only the most engaged recipients with the goal of reducing the volume by half or more until you see results begin to overperform. 

Seeing open rates consistently low across all providers does not necessarily mean mail is going to spam. Sometimes, messages do reach the inbox but simply don’t generate many opens. Other times, there can be issues that obscure open tracking such as disable images or technical issues. If you feel most all mailbox providers are filtering your messages to spam, it’s critical that you make significant changes to how addresses are collected and who you are targeting so that you prevent spam complaints and only send messages to recipients that want them.

Spam Complaints

Seeing recipients mark the one of the first few messages from you as spam indicates recipients are receiving mail they don’t feel like they signed up for. Make sure everyone you send to has opted in directly and specifically to receive mail from the brand in the form information of your message.

Seeing spam complaints increase for recipients who have been receiving from you for some time often indicates that you are sending too much mail or that your messages have become irrelevant to recipients. Adjust how often and how long you send to unengaged recipients to limit the negative signals your mail is generating. 

Gather insights

Understand Subscriber Intent 

Be able to identify recipients that become new subscribers during the holidays as you may want to message them differently, especially after the holiday season.

Let subscribers take a break 

If recipients are bothered by the amount or the content they are receiving from you, it is much better to honor their wishes and temporarily pause or reduce their frequency compared to them registering a spam complaint or unsubscribing permanently.

Document as you go

Keep records of your email deliverability stats by day or week so you can look back at them to understand:

  • What types of offers/campaigns performed the best
  • What types of volumes you were sending and how that impacted results
  • How different mailbox providers treated your mail
  • What types of sending tactics generated high complaint rates vs those that performed well
  • Make note of any deliverability challenges and how you addressed them

What to do after the holiday season

Take time to recover and repair

If you ramped up holiday volumes and frequency over the holiday sending period, it is likely that your sending reputation across the different mailbox providers is not as healthy as it was pre-holidays. 

Plan for a period of time in your marketing schedule to allow for more conservative targeting strategies that reduce your volumes somewhat while targeting your most engaged recipients. Focus your content and CTAs to be as compelling and engaging as possible. 

Remember that recipients are tired, too.

Re-permission holiday addresses and newly reengaged addresses

It is likely that your subscriber list grew over the holiday season. However, not all of these subscribers are ones who are engaged with your brand year around. 

Consider special messaging to those recipients that collects information about their interest. Offer an option to pause their email subscription until the next holiday season or just around holidays.  If you see elevated rates of complaints among the cohort of new addresses, consider sending them a campaign asking recipients to take action to confirm their interest in receiving email from your brand.

Start preparing for next year

Write down what you learned, what worked, what didn’t work, and any other notes about the holiday sending season. Add those to a file along with your stat tracking and deliverability results. It’s amazing how helpful that will be in seven months when it is time to repeat all of this.

Consider what data points would’ve been nice to have going into this season and begin collecting them now. 

Identify the point in the next year where you will begin your preparations for the 2024 holiday season while your perspective is still fresh.

Happy holiday sending!

Case Studies

Request a Demo