Second wave email: how to lift click-through rate by up to 83%

A second wave email is a follow-up for people who did not respond to the first one. In our own campaign, resending the email to those who did not open it raised the click-through rate by 22%. In another campaign, a reminder to those who did not click raised it by 83%. Both take a single automation and a few minutes to set up. In this article you will find both campaigns with their numbers, step by step setup, the right timing and the reason why a second wave based on clicks pays off more today.

In a nutshell

1. In the examples in this article, the second wave went to 1,114 of 1,465 people and to 2,108 of 2,491 people. Those who responded received nothing extra.
2. Resending to those who did not open brought our campaign 16 extra clicks and lifted the click-through rate from 5.1% to 6.2%.
3. A reminder to those who did not click brought 324 extra clicks and lifted the click-through rate from 15.7% to 28.7%.
4. A reminder based on clicks is more reliable today. Apple Mail counts emails as opened automatically, so most of its users do not fall into the "did not open" group.
5. Send the second wave once, with a new subject line and usually one to three days later.
6. Measure success by the total clicks from both emails, not by the click-through rate of the second wave alone.

In short: what it is, when to use it, how much work it takes and what can go wrong

• What it is: an automatic follow-up email for recipients who did not open the first email or did not click.
• When to use it: for emails with a clear goal, such as an invitation, an offer, a registration or a survey.
• How much work it takes: a resend takes five minutes to set up, a reminder also needs a short new email.
• What can go wrong: more unsubscribes and spam complaints, and a resend will not reach most Apple Mail users.

What has changed since the article was published: The article came out in September 2021 under the title "2 concrete examples and guidelines on how to increase the click-through rate by 20% or 80% via automatization". In October 2026 we rewrote it. These are Quanda's own campaigns and their data stayed the same, and we corrected the description of the recipient group in the second campaign (it went to those who did not click, not to those who did not open). The article now explains the impact of Apple Mail Privacy Protection, which came into effect in September 2021, after both campaigns had been sent. We also added a six step guide, timing advice, how to calculate the result and the most common mistakes.

What a second wave email is

A second wave email is a follow-up email sent only to the campaign recipients who did not respond to the first one. In Quanda, you set it up as an automation in a simple email campaign. After the time you choose, Quanda picks out who did not respond and sends them a prepared email. You do not have to keep an eye on anything or select recipients by hand.

A second wave email is also called a resend, a follow-up email or a reminder email.

The second wave comes in two versions, and each suits a different purpose.

Both versions are part of email automation that you set up once and that then works for you. The second wave is the quickest of them all. You need no new content, no new database and no new contacts, you simply give a second chance to people who already know you.

Why the click-through rate matters most

Every email campaign has a different goal. Some inform, others sell. One of the most important metrics for judging campaign results, though, is always the number of clicks.

The click-through rate (CTR, also called click rate) is the share of recipients who clicked a link in the email out of all delivered emails. The higher it is, the more people took the next step towards a purchase, an order, a registration or whatever other action you expect from the email.

The open rate is a less reliable metric today. Apple Mail Privacy Protection downloads email content automatically in the background, whether or not the person actually opens it. Such an email then counts as opened. According to Litmus, Apple accounted for 62.26% of all email opens in July 2026, and Apple's privacy protection affects roughly 55 to 60% of opens (Litmus Email Client Market Share). A click, on the other hand, can only come from a person.

To give you an idea of what a typical click-through rate looks like:

Sources: MailerLite, Email Marketing Benchmarks 2025 (3.6 million campaigns); Mailchimp, Email Marketing Benchmarks; GetResponse, Email Marketing Benchmarks 2024 (4.4 billion emails). GetResponse also counts repeated clicks, which is why its figure is higher.

The campaigns in both examples had an above average click-through rate the first time round. Even so, the second wave added dozens and hundreds of clicks that would otherwise have been left on the table.

Example 1: resending to those who did not open

At Quanda we sent our own campaign to just under 1,500 recipients. Just under a quarter opened it and 75 people clicked. Three days after sending, Quanda automatically sent the same email to everyone who had not opened it.

The total click-through rate is calculated from the emails delivered in the first campaign: 91 clicks out of 1,465 delivered is 6.2%. Compared with the original 5.1%, that is 22% more.

On its own, the second wave looks weak, with a click-through rate of 1.4%. That is fine, though. It targets people who missed the first email, and every click from them is pure extra gain. For five minutes of work it brought 109 more reads and 16 clicks.

Watch out for Apple Mail: The data come from March 2021, before Apple Mail Privacy Protection. Today, most Apple Mail users are counted as having opened the email, so they will not receive the resend. Mailchimp says so explicitly in its help on Apple privacy and recommends building automations on clicks instead (Mailchimp, Apple Mail Privacy Protection FAQs). The "did not open" group is therefore smaller today and the result of a resend tends to be more modest.

Example 2: a reminder to those who did not click

We sent our second own campaign to two and a half thousand recipients. The result was excellent from the start: almost half opened it and the click-through rate was 15.7%. Three days after sending, everyone who had not clicked the main link received a short reminder.

The reminder went to 2,108 people, seven more than the number of delivered recipients who did not click (2,101). In the meantime, the temporary block after a soft bounce expired for a few contacts and Quanda returned them to the mailing.

714 clicks out of 2,491 delivered is 28.7%. Compared with the original 15.7%, that is 83% more.

The most interesting part is that the reminder had almost the same click-through rate as the first email. People were interested in the offer, they had just put it off the first time. All they needed was a reminder that something was waiting for them.

The reminder reaches two groups of people: those who never opened the first email and those who read it but did not click. Write it so that it makes sense to both. Keep it short and clear, with one prominent link and a reason to click right now.

How to set up a second wave email in 6 steps

The steps are the same for both versions, only the condition and the email content differ.

1. Decide who the second wave is for: those who did not open the email or those who did not click the main link.
2. Prepare the second wave email in the Transactional e-mails section. For a resend, load the original campaign saved as a template, for a reminder, write a shorter email with one prominent link.
3. Change the subject line so that it differs from the first version.
4. Save the transactional email, send yourself a test and activate it in the Campaign activation section.
5. In the original campaign, open Automation, add the condition "did not open the e-mail" or "did not click a particular link", set the time and choose sending the prepared transactional email as the action.
6. Send the original campaign and, once the second wave has gone out, add up the clicks from both emails and divide them by the number of emails delivered in the first campaign.

Save the original campaign as a new template once it is finished and tested. The transactional email is then an exact copy of it, with all the texts, images and links. How transactional emails work is explained in the guide Transactional e-mails.

The time is counted from when the original campaign was sent. With the conditions "did not open the e-mail" and "did not click a particular link", the second wave goes out to everyone at once, exactly the set time after the first campaign was sent. The details are in the guide Automation in a simple campaign.

Try a second wave in Quanda

When to send the second wave

There is no single rule, and providers' recommendations differ.

Sources: Mailchimp, Resend an Unopened Email; MailerLite help on automatic resending (June 2026); Omnisend, blog post on resending a campaign (May 2024); Constant Contact, knowledge base.

In practice, let the content of the email guide you. For an invitation or a time-limited offer, send the reminder so that people still have time to respond, ideally two to three days before the deadline. For a newsletter or news, a day or two is enough. A second wave that arrives after the event has taken place makes no sense.

When not to send a second wave

• Twice or more. There is one second wave. A third and fourth repeat is more likely to annoy people and push up spam complaints.
• Both versions for one campaign. Anyone who did not open did not click either. With both conditions, the same people would receive two extra emails. Pick one.
• Emails with no value for the recipient. A second wave amplifies whatever is in the email. If the first version did not catch people's attention, the second one will catch it even less.
• After the deadline. A reminder for an event that has already happened looks unprofessional.
• Without a new subject line. The same people will miss the same subject line a second time for the same reason. How to write a better one is covered in the article How to write an email subject line people actually open.
• To people who have not responded for a long time. If someone has not opened your last ten campaigns, a second wave will not wake them up. Such contacts belong in a re-engagement campaign or out of your database.

Tip: Keep an eye on spam complaints. Google wants bulk senders to keep them below 0.1% and never reach 0.3% (Google, Email sender guidelines). A sensibly sent second wave will not push them up, but repeated pestering will. More in the article What spam is and 4 rules to keep emails out of spam.

Checklist before launching a second wave

• I know whether the second wave targets those who did not open or those who did not click.
• The second wave email has a new subject line.
• The reminder has one prominent link and makes sense even to those who did not read the first email.
• The transactional email is activated.
• The second wave goes out early enough before the event or offer deadline.
• Only one version of the second wave is set up for the campaign.
• After sending, I will add up the clicks from both emails and compare them with the first campaign.

Final thoughts

A second wave is the cheapest way to get more out of a campaign. You need no new contacts and no new content, you just give a second chance to people who know you and missed the first email. Start today with a reminder to those who did not click. It is more precise and in our example it brought almost twice as many clicks.

You will find more automations that work for you, from a welcome email to birthday wishes, in the article Email automation: 8 scenarios that work for you and in the free online course Automation in Quanda from A to Z. If you would like to set up a second wave with us, book a free consultation or write to us at support@onquanda.com.

Fingers crossed for you!