Email deliverability: Fixing the dilemma undermining Market Research response rates

What dictates whether your survey lands in the inbox or disappears into the void?

With ISPs tightening rules, spam filters getting smarter, and low engagement signalling the delivery death knell, even well-designed studies can fail before they begin. So what can you do about it?

In a recent webinar, Forsta’s Bradley Gerkens, Global Director for Fieldwork and Delivery and an expert on email deliverability, unpacked the drivers behind declining deliverability and what it means for data quality, fieldwork efficiency, and ultimately, business outcomes. Here, he answers some of the burning questions from our webinar attendees.

Read on to discover best practices for email deliverability in 2026 and beyond, and the hidden factors sabotaging your survey invites.

You can also watch the full on-demand webinar here.

Let’s start with the biggie: Is email dead?

This is a great question, but we’re not ready to throw the baby out with the bathwater just yet. If email invites weren’t still an important part of market research, this conversation wouldn’t be happening.

Unfortunately, there are a lot of researchers who do this part terribly and feel duly frustrated with the results, but that does mean easy opportunities for quick wins. If researchers follow best practice, the ROI for email as a delivery mechanism has long been proven.

So, until we find or invent a better mousetrap, email is here to stay.

How do you measure domain reputation?

Google Postmaster Tools is free, easy to set up, and gives you a clear reputation rating (High, Medium, Low, or Bad) straight from Gmail. Since Gmail is one of the biggest email providers out there, this is a great place to begin. Microsoft offers something similar called Sender Dashboard for Outlook users, so it’s worth signing up for that too. 

Websites like SenderScore.org and MXToolbox let you check your domain’s health in just a few clicks. SenderScore gives you a score out of 100, while MXToolbox lets you know if you’ve landed on any blacklists. Think of these as quick, free checkups to make sure your emails keep landing in inboxes. 

You should also track important stats like bounce rates, spam complaints, and open rates. These numbers offer critical feedback and tell you a lot about your domain reputation. If you want to avoid a negative reputation, keep your bounce rate under 2% and spam complaints below 0.1%. If people are opening and clicking your emails, that’s a strong signal you’re doing things right! 

How do you ‘warm up’ a new domain?

It’s important to build up a new domain gradually so that mailbox providers – like Gmail, Microsoft and Yahoo – see consistent, legitimate sending behavior. The same applies with B2B sending. 

If the IP is already completely seasoned and warm, you can effectively start Day 1 with ‘X’ and double that volume every day thereafter. The ‘X’ is a variable that depends on many client-specific considerations, so there’s never a hard-set rule or value for this.

Is it better to have a weekly blast or multiple sends per day?

A consistent and predictable cadence is best practice. Significant spikes in volume trigger ISPs to hold (‘defer’) emails for delayed delivery until user engagement can be determined. Or they may even block the emails outright – especially when you’re dealing with B2B domains, which can be more sensitive to a volume spike. 

How many email addresses should you include in a batch send?

Think quality over quantity. Sending smaller, well-timed batches keeps your domain reputation healthy, avoids mailbox provider throttling, and gives you the ability to catch problems early. It’s not about sending less; it’s about sending smarter.  

For senders intent on protecting their reputation, the 100/5 rule is considered industry best practice: no more than 100 emails per inbox per day to no more than 5 inboxes per domain. This means you’d ideally cap your daily sending at around 500 emails (100 × 5 inboxes) per domain.

Staying within these boundaries significantly reduces the risk of being throttled or flagged by mailbox providers. 

Is ‘one-click unsubscribe’ necessary to achieve good deliverability?

A ‘one-click unsubscribe’ option demonstrates authenticity and legitimacy, but for bulk senders, it isn’t simply a nice-to-have. It’s mandatory. 

A bulk sender is defined as anyone sending more than 5K emails to private mailbox providers from a single domain.

Not only is ‘one-click unsubscribe’ a prerequisite for emailing providers such as Yahoo, Microsoft and Gmail, it’s actually a legal requirement in areas like North America. Failure to comply risks having your emails blocked outright and damaging your reputation amongst the various mailbox providers.

How important is the use of https for all links compared to http when it comes to deliverability?

All links, including those hardcoded into the html, can severely impact delivery. This is especially true for B2B sends. However, this won’t specifically damage domain reputation or cause emails to be blocked; it can simply contribute a minor addition to an overall spam score. So, if a secure website can be provided, it’s recommended to do so. 

If a researcher wanted to avoid traditional survey subject lines in favor of something more engaging, what would you suggest?

Seek to provoke curiosity. The goal is to give recipients a reason to stop, engage, and avoid hitting the spam button. So many email subject lines are too generic, and terms like ‘survey’ and ‘feedback’ are so prevalent that they’re easily ignored.

Try to personalize and provoke by using details, such as a specific product or location, and posing the subject as a question. So instead of “We value your feedback!”, try “Hi Jane, how was your visit to our location?”  

Should researchers use their own corporate email server (survey.corporate.com domain), or Forstas’s built-in email server (euro.confirmit.com)?

We’d always recommend delegating to a custom subdomain and pointing it to Forsta’s email servers, as this allows your emails to contain branded URLs. As you already own the domain, there’s no additional cost associated with this.

The benefit of a unique subdomain (vanity url) is tied to both branding and increased control over domain reputation. For those with consistent and significant sending volumes, a unique subdomain allows you full control over how mailbox providers receive your emails. More importantly, it can also build trust with an opted-in recipient who’s expecting your email, and therefore more likely to engage. 

Is it preferable to send survey invitations from a client’s email domain, as respondents already know and trust the sender?

Assuming it’s properly configured, a branded subdomain (e.g. mail.clientemaildomain.com) is always the best option as this breeds familiarity and trust with recipients who’ve already interacted and opted into receiving emails.

If clients supply a list of recipient email addresses but engagement data is lacking, what should you do?

In 2026 and beyond, engagement is highly scrutinized by advanced machine learning algorithms. The first and simplest method to prevent potential engagement issues is to verify your email sample through an online verification tool, such as Debounce or Brite Verify. This will help you to weed out aged, expired, or full email boxes. Or even worse, ‘spam traps’ – inactive emails used by mailbox providers to flag potential spam accounts. 

Ideally, emails should be checked and verified 24-48 hours prior to sending, but a concerning majority of bulk senders neglect to follow this very simple practice. 

If you’re already following best practice and still not seeing an improvement in response rates, what’s next?

The only way to improve your response rates is to find out what you don’t know. The solution to improved response rates isn’t necessarily a technical one; it’s a marketing one. And that’s where A/B testing comes into play. No single solution works for any one campaign or segment, so you have to experiment. 

When deciding on subject lines or email copy, ask yourself, “would I want to receive this email?” Send the email to your own inbox and see if the subject line catches your eye. You want to avoid generic, overly formal content that’s drowning in platitudes. “We value your feedback” might be sincere, but it doesn’t feel remotely personal.

Utilize your data and segment to create a unique message that feels like someone just clicked send to reach that one recipient. And once you’ve come up with the new format, test it out. Find out how adding a name or location in the subject line affects engagement. See how changing the placement, text, or color of your CTA affects response rate. Keep testing, keep iterating, and keep learning!

Inbox placement isn’t luck; it’s good practice, done consistently. To get started, reach out to your account manager. Not yet a customer? Speak with an expert here. And that remains a profoundly human capability; one that isn’t becoming easier to automate.