A Sequence only works if people see it. The deliverability check uses AI to review your Sequence against deliverability best practices, based on the sender guidelines from Gmail, Yahoo and Outlook.com and Mixmax's own recommendations. It flags what inbox providers and recipients tend to treat as a red flag, like vague subject lines or follow-ups that say the same thing twice, and suggests a fix for each one so you can clean things up before they cost you replies.
Beta: The deliverability check is part of the Sequences beta. Once your workspace is in the beta, turn on Sequences Redesign in Mixmax Labs.
How to run a check
You can run a check whenever you want, before or after you activate.
Open your Sequence in the new editor.
Select an email stage and click Check deliverability at the bottom of the editor. On automated email stages, it's next to Send test email. You can also open the Deliverability tab in the side panel, next to Stage settings, from any stage.
The first time you check a Sequence, click Run check.
The check reads the saved version of your Sequence. If you have unsaved changes, Mixmax asks whether to save first. Click Save & check to save and run it, or Keep editing to go back.
While it works, you'll see Analyzing your sequence…. You can leave the page and come back. Your latest results stay in the Deliverability tab, along with when the check ran.
Changed the Sequence since your last check? You'll see Sequence changed since this check. Click Run new check to look at the latest version. If nothing has changed, click Re-check to run it again.
What the check looks at
The check compares your Sequence to deliverability best practices in three areas: your emails, a few Sequence settings and your domain's email authentication.
Your emails
The check reviews every email in your Sequence: automated emails, manual emails and each active version of an A/B test. Calls, to-dos, LinkedIn, SMS and other non-email stages aren't part of the check, and neither are A/B versions you've turned off.
In each email, it looks for:
Subject lines that are unclear, don't match the email, lean on lots of punctuation or urgency, or start with "Re:" or "Fwd:" when the email isn't really a reply or forward
Emails that don't give the recipient a clear reason to engage or a clear next step, or that come across as pushy
Variables that look broken, and personalization that claims something about the recipient you can't back up (the check can't see your recipients' actual values)
Formatting that gets in the way, like emails that are mostly images or hidden text, heavy styling, or links that aren't needed or clear
Follow-ups that repeat earlier emails instead of adding something new
Sequence settings
It looks at your open, link and file tracking, and whether Mixmax's automatic unsubscribe link is on.
Email authentication
It checks whether your sending domain is set up for email authentication, which helps inbox providers trust that your emails really come from you. Your IT team or domain admin usually manages this.
Reading your results
Your results open with a short summary and a count of what to fix and what's working, for example 2 to fix and 3 strengths. Below that you'll find:
Up to 8 things to fix. Each one explains what the check noticed and gives you a Fix. The label next to it shows which stage (and A/B version) it's about, and clicking the label takes you straight to that stage.
What looks good, with up to 5 things you're already doing well.
A line about your domain's email authentication.
A short note on what the check covers.
If there's nothing to fix, you'll see No content issues found.
Think of the results as coaching based on best practices, not a spam score. There's no number or pass/fail grade, and the check never changes your Sequence or stops you from activating. You decide what to fix.
Run it from your AI assistant
If you've connected Claude or another AI assistant to Mixmax through the Mixmax MCP, you can ask for a deliverability check right in chat. For example:
"Check the deliverability of my Webinar Invite sequence."
"Rewrite the stage 2 subject line based on what the deliverability check flagged."
Your assistant checks the saved version of your Sequence and gets results for each stage, including each A/B version. These checks count toward the same limits as checks in the editor, and they show up in your Deliverability tab too.
FAQ
Why can't I find or use the Check deliverability button?
You're in the previous editor. The check is only in the new Sequence editor, so make sure Sequences Redesign is on in Mixmax Labs.
You've selected a non-email stage. The button only shows on email stages. Pick an email stage, or open the Deliverability tab in the side panel.
Your organization's AI policy turns off AI features. The button and tab show up greyed out, and hovering over them shows Not available due to your organization's AI policy. The policy also blocks checks from AI assistants. Talk to your workspace admin if you have questions.
What if my Sequence doesn't have any email stages yet?
Add at least one email stage first, since the check only reviews emails. If you run it without one, you'll see No content issues found because there wasn't anything to review.
Does a clean result mean my emails will reach the inbox?
Not by itself. The check covers your emails, a few Sequence settings and your domain's email authentication. How much you send, your domain's reputation and bounces from bad addresses matter too. Optimizing email deliverability covers the rest, including how to keep an eye on your reputation with Google Postmaster Tools.
How is this different from the authentication warning when I activate?
The authentication warning checks your domain's email authentication right before a Sequence starts sending, for Google Workspace accounts on a company domain. The deliverability check is something you run while you build, and it's mostly about what your emails say and how they're put together. It's best to use both.
Is there a limit to the number of checks I can do?
Yes, if you make too many requests you will see a message letting you know. Give it a little while, then run the check again later.