Hi there - thanks for your question. A few things that could be causing this issue. Here are some solutions:
Verify Email Sending Eligibility
Even if the flow preview shows that an email should have been sent, Klaviyo may not send emails due to the following reasons:
A. Check Suppression & Marketing Consent
- Go to a customer’s profile and check their status:
- Unsubscribed or suppressed users won’t receive emails.
- Ensure they are marked as “Subscribed” to email marketing.
- Segment might include non-marketable profiles:
- If the segment includes suppressed or transactional-only profiles, they won’t get the email.
- Solution: Add a filter to exclude suppressed users: Properties about someone > Can Receive Emails = TRUE
B. Review Email Sending Limits
If you have Smart Sending enabled, it may block emails to users who received another email recently.
Solution:
- Disable Smart Sending for this flow (edit the email inside the flow and toggle “Ignore Smart Sending” ON).
- If there’s a sending limit for the day, Klaviyo may skip sending to some users.
- Check Account Settings > Email Limits to verify if your sending limit was reached.
C. Review Flow Activity Logs
- Go to the Flow > View Analytics > Recipient Activity.
- Check if the missing users appear under:
- “Skipped” – Shows why emails were not sent.
- “Bounced” – Indicates an email delivery issue.
- “Failed” – If Klaviyo had issues sending the email.
If you are still having issues please let me know and I can provide additional support.
Hi @R_Javarus
To add to what @zacfromson outlined above as possible causes for not all users to be sent the email, I had one additional thought. In your description, you mentioned the flow is based on a segment. If this is a flow you have had running for a while, or perhaps the segment has been assigned to the flow for a while (even if the segment conditions have changed), when a segment is used as a flow trigger, contacts can only be entered into the flow once.
So, its possible, if the flow/segment has been used for a while where contacts could have been entered more than once, on the second instance, those contacts would be ignored.
For birthday, or any date-specific type flows, rather than use a segment, you may want to consider using a date-based trigger for your flow. This uses a date saved as a profile property, and will trigger on or before that date (depending on your settings). But, the nice part is, you can set a repeat function with a date-based trigger. Which for birthday flow, is helpful to resend an email to the same contact if their birthdate has come around again.
There are a few possible reasons for why some of your contacts haven’t receive the email, and I hope between @zacfromson and this, you’ll be able to identify and resolve the issue.
Thanks!
@In the Inbox
Hi @zacfromson Thank you for your comment. These all seem to be in order, so still not sure why some people are not sent to.
@In the Inbox Thank you for your comment, I wasn’t aware of this. I’ll take a look and test the flow with this setting.
Hello @R_Javarus , It sounds like a sending delay or suppression issue. First, check Klaviyo’s email queue to see if the emails are still pending. Also, verify the account’s daily sending limits under "Email Settings." If limits aren’t the issue, check if those contacts were recently suppressed (e.g., unsubscribed, bounced, or marked as spam). Lastly, confirm that Smart Sending is turned off for this flow, as it may prevent emails from being sent if contacts received another email recently. Let me know if you need further help!
