Improving email deliverability

A practical guide to getting your emails seen in 2026

Getting your emails into your subscribers’ inboxes is essential for building trust, increasing engagement, and growing your business. Inbox providers like Google, Yahoo and Outlook often adjust the algorithm that determines inbox placement of your emails, so it's important that you continuously monitor your analytics and stay up to date with deliverability best practices.

Even if you haven’t changed anything, new rules and filtering systems may still affect where your emails land.

• Email delivery = your email was accepted by the recipient’s mail server.

• Email deliverability = where that email lands after delivery (inbox, promotions, or spam).

You can have a high delivery rate and still have deliverability issues if emails aren’t being seen.

Note: Emails sent via Flodesk (and any email marketing platform) are treated as marketing emails by inbox providers.

When an email arrives, inbox providers ask:

• Is this sender trustworthy?

• Do people want these emails?

• Are recipients engaging—or ignoring them?

Your inbox placement depends on how you answer those questions over time.

The main factors are explained below.

A custom domain means that you’re sending emails from a personalized, unique web address that you own. For example, Flodesk owns the domain “flodesk.com” and one of our domain emails is “hello[at]flodesk.com”.

This is different from a free email address, which is provided by services like Gmail, Yahoo, or Hotmail. Examples include you@gmail.com, you@yahoo.com, and you@hotmail.com.

Sending from a free email address is a common spammer behavior and may result in:

• Messages going to spam folders

• Emails being blocked from delivery altogether

• Damage to your sender reputation

To add your custom domain email address to Flodesk, go to Account settings > Email setup. Once done, your domain will be available for authentication under Account settings > Domain setup.

Domain authentication proves your emails are really coming from you. In 2026, this is no longer optional. Authentication includes:

• DKIM – verifies the email wasn’t altered

• SPF – confirms which servers can send on your behalf

• DMARC – tells inbox providers what to do if something looks suspicious

Learn more in How to authenticate your custom domain manually and How to automatically configure your domain

Why this matters:
Unauthenticated emails are more likely to be filtered or rejected before reaching inboxes.

Your sender reputation is like a credit score for your domain. Inbox providers build it based on factors like:

• Opens and clicks

• Replies to sender

• Marking an email as important

• Moving it from spam to inbox

• Spam complaints

• Bounce rates

• Sending consistency

• Authentication status

A strong sender reputation improves inbox placement. A damaged one makes recovery harder.

These signals tell inbox providers your emails are wanted:

• Strong engagement
  Subscribers open, click, reply, or interact with your emails regularly.

• Sending to engaged subscribers first
  You prioritize people who have recently interacted with your emails.

• Consistent sending behavior
  You email on a predictable schedule without sudden spikes in volume or long gaps.

• Proper domain authentication
  Your sending domain is authenticated (SPF, DKIM, DMARC).

• Low bounce rates
  Most emails are delivered successfully to valid addresses.

• Clear permission and expectations
  Subscribers knowingly opted in and understand what they’ll receive.

These signals increase the risk of spam placement:

• Low or declining engagement
  Many subscribers ignore or delete your emails over time.

• Emailing large groups of unengaged subscribers
  Repeatedly sending to people with no recent activity is a major red flag.

• Spam complaints
  Subscribers mark your emails as spam instead of unsubscribing.

• Sudden volume changes
  Large increases in send size or frequency without warming up.

• Sending after long pauses
  Emailing your full list after months of inactivity without warming up again.

• Missing or broken authentication
  SPF, DKIM, or DMARC isn’t set up or stops passing.

• Purchased or scraped email lists
  Emails sent without clear, explicit consent.

Inbox providers look at patterns, not individual subscribers.

For example:

If you send an email to 1,000 people and only 100 engage, inbox providers see that most recipients didn’t interact with the email.

But if you send the same email to 100 people and most or all of them engage that tells inbox providers the message was wanted and valuable.

From an inbox provider’s perspective, sending to fewer engaged subscribers is often healthier than sending to a much larger, disengaged audience.

This is why focusing on your most engaged subscribers, especially when deliverability is shaky, can quickly improve sender reputation and future inbox placement.

Subscriber behavior strongly affects deliverability, but engagement data is no longer perfect.

Privacy protections from Apple Mail, Gmail, and others mean:

• Opens and clicks aren’t always tracked

• Some subscribers read emails without triggering activity

• Quiet readers absolutely exist

That’s okay.

Inbox providers still see many signals that email platforms can’t, such as reading time, scrolling, moving emails between folders, or marking emails as important.

Deliverability today is about reducing risk signals, not identifying every individual perfectly engaged reader.

Instead of thinking “remove,” think temporarily exclude.

Inbox providers look at who you’re actively emailing right now.
Sending repeatedly to large groups showing no detectable engagement is a major risk signal.

• Create a segment of subscribers with no recent activity (30–60 days is a common starting point)

• Exclude this segment temporarily from regular sends

• Continue sending to your most engaged subscribers first

• Gradually reintroduce excluded subscribers once engagement stabilizes

Excluding subscribers is not the same as unsubscribing them and doesn’t have to be permanent.

There’s no perfect number:

• 30 days → more aggressive, good for frequent senders

• 45–60 days → safer for less frequent sends

• 6+ months → likely disengaged for most lists

What matters most is avoiding repeated sends to large, unresponsive groups.

Learn how to find unengaged subscribers in Identifying and managing unengaged subscribers in Flodesk

Replies are one of the strongest engagement signals inbox providers see, even though they can’t be tracked inside Flodesk.

If someone replies:

• They are highly engaged

• Add them to a “Warm” or “Highly Engaged” segment

• Continue sending to them regardless of open/click data

If you run a re-engagement campaign and subscribers reply or click to stay, you’re doing the right thing.

Learn How to Make a Button or Link Trigger an Email Reply in Flodesk

Inbox providers prefer predictable behavior.

• Send at least once per month (weekly or biweekly is even better)

• Avoid sudden volume spikes

• Don’t email your full list after a long pause

• If increasing volume, start with engaged subscribers and grow gradually

If your domain hasn’t sent emails in months, treat it like a new sender. Even sending gaps of 4-6 weeks may require a gradual warm-up to rebuild sender reputation:

• Start with small, engaged segments

• Gradually increase volume

• Rebuild trust slowly

Learn more in Warming up a new sending domain

Transition slowly and don’t switch overnight to protect your deliverability.

A safe approach:

1. Email your engaged subscribers from Flodesk still using your free gmail.com email address and let them know your sending address will change

2. Ask them proactively to add the new address to contacts

3. Add and authenticate your new custom domain in Flodesk

4. Send first emails from the new domain only to engaged subscribers

5. Encourage replies

6. Gradually expand volume over time

This protects what’s already working while setting you up for long-term success.

Content still matters. Especially when trust is being rebuilt.

• Avoid misleading subject lines

• Use clear, honest language

• Don’t rely on images alone

• When using images, always include alt text

• Avoid link shorteners (use full URLs, especially for YouTube)

• Encourage replies or clicks

Learn more in Common reasons emails may land in the spam folder

Email has become more complex, but it still works. What’s changed isn’t the channel. It’s the visibility into individual actions.

Focus less on any single metric and more on patterns over time:

• Replies

• Purchases

• Bookings

• People telling you they love your emails

If email is driving real outcomes, it’s doing its job.

• Add a custom domain email address under Account settings > Email setup

• Authenticate your sending domain under Account settings > Domains setup

• Send only to opted-in subscribers

• Focus on engaged subscribers first

• Temporarily exclude unengaged subscribers when needed

• Warm up domains after long sending gaps

• Send consistently and avoid sudden spikes

• Use clear, honest content and full, not shortened links

Deliverability isn’t about perfection. It’s about trust, consistency, and sending emails people want.

What’s the difference between delivery and deliverability?
Delivery means the email reached the mail server. Deliverability means where it landed, such as inbox, promotions or spam.

Do I need to delete unengaged subscribers?
Not necessarily. Temporarily excluding them from sends could be enough to protect deliverability.

Are opens and clicks reliable?
Not fully. Privacy protections limit visibility. Inbox providers still see engagement signals even when platforms don’t.

Is a small list with good engagement still at risk?
Less so, but it’s still a good idea to regularly review engagement and maintain list hygiene.

Should I warm up my domain if I haven’t emailed in a while?
Yes. Even sending gaps of 4-6 weeks may require a gradual warm-up to rebuild sender reputation.