Peak sale seasons (Black Friday, New Year's, International Women's Day) are golden opportunities for e-commerce, but they're also the toughest test for marketers and technical infrastructure alike. The volume of emails hitting inboxes spikes sharply, spam filters switch into a stricter mode, and delays in sending queues can derail even the most carefully planned campaign.
To make sure your holiday campaigns deliver revenue instead of technical headaches, you need to "crash test" your infrastructure before the rush begins.
1. Technical infrastructure and load management
During peak load hours, sending queues on the sender's side or on intermediate servers get overloaded, which can delay emails by 15–20 minutes. For a regular digest, that's annoying, but if a transactional email is delayed (say, a login code or an order confirmation), the business loses customer trust and money.
What's important to do at this stage:
- Separate your sending streams. The most common mistake is sending transactional (service) and marketing (promo) emails from the same domain. If your domain's reputation drops because of complaints about a mass sale campaign, it will instantly block delivery of critical confirmation codes too. Make sure to separate the streams and send transactional messages from a dedicated subdomain.
- Check queue prioritization. Service messages need to go out instantly, processed in a priority queue. If they're sitting in the same line as a million-strong promo list, delays are inevitable.
- Monitor your limits. Recipients' mailboxes can get full during this period, and servers will reject emails, returning a delivery error. Timely monitoring of hard bounces helps you clean the list in time.
2. Deliverability and spam filters: how to avoid getting flagged
Modern spam filters analyze an email holistically, relying primarily on sender reputation and domain/IP history, rather than individual trigger words. A sharp spike in email volume during the holidays is a major trigger for automated systems, signaling a possible spam attack.
To protect your reputation, check the following:
What to check | What it does | Why it's critical during peak season |
|---|---|---|
The SPF record | A list of servers allowed to send emails on behalf of the domain. | Without it, emails get flagged as suspicious at the receiving server level. |
The DKIM signature | A digital signature confirming the email was actually sent from your domain. | Guarantees email providers that the content wasn't altered in transit. |
The DMARC policy | Tells the recipient's server what to do with emails that fail SPF/DKIM checks. | Without this trio of records configured, emails are very likely to land in spam. |
Postmaster monitoring | Connecting Postmaster Tools from Gmail and Yandex Mail. | Lets you track domain reputation and the spam complaint rate in real time. |
3. Templates and content: a test of visual resilience
Even if an email is technically delivered, it can still "break" visually. Different email clients use different engines to render HTML, so the same template looks different in Outlook, Gmail, or Apple Mail.
Before sending peak campaigns, audit your content:
- Test email rendering. Check how the email looks across various clients and on mobile screens before the actual launch. Specialized platforms like Letteros let you quickly open the "Testing" section right in the editor, run renders, send a test email, and run a spam check.
- Check product cards and prices. Holiday emails often use dynamic product blocks. Make sure prices and stock levels are current. Using automatic product card parsing in Letteros lets you pull current data (photo, price, stock) directly from the site with no manual coding, eliminating human error.
- Total UTM tag coverage. Every link inside the email (including the logo in the header and banners) should have unique parameters. Without this, your analytics will be incomplete and you won't know which campaign or element actually drove sales.
What to check before launching a peak campaign: a checklist
— Streams are separated: marketing promo traffic runs separately from transactional notifications and login codes. — DNS records are configured: SPF, DKIM, and DMARC are correctly set and valid. — List hygiene is done: inactive addresses that haven't opened or clicked your emails in a long time are temporarily excluded, to reduce the risk of complaints. — Renders are checked: the template has been tested in Outlook, Gmail, and on mobile devices, and the layout doesn't break. — Product card data is synced: emails display current prices, and in-stock items match the site's actual inventory. — UTM tags are set: automatic tagging or manual tagging works for every link in the email template.
Bottom line
Peak season doesn't forgive sloppy technical prep. Separating sending queues in time, authenticating your domain, and thoroughly auditing your templates are the basic steps that protect your campaigns from landing in spam or hitting technical delays. Running a crash test lets you go into the holiday rush fully prepared, guaranteeing stable inbox delivery and maximum conversion into sales.
Also read on our blog:
- How to Announce a Sale by Email: Campaign Structure From Warm-Up to the Final Email
- Seasonal Campaigns: How to Prepare Emails for New Year's, International Women's Day, and Black Friday in Advance
- How to Automate Adding UTM Tags to Emails
- How to Test Email Renders in Letteros
🚀 Want to prepare your campaigns for peak loads and guarantee inbox deliverability?