On the Folderly Premium chart, there are 4 statuses for emails:
In this article, I want to shed more light on the "Undelivered" section.
Undelivered emails - emails that were sent from your mailbox but weren’t received by our recipients yet.
Usually, you may see emails distributed in the "Undelivered" at the middle of the day when the Spam Fix is still running. In this case, you shouldn't worry about it as in 98% of cases our recipients just haven't found them yet in their mailbox. Once the email is found it will be redistributed to either "Inbox", "Promotions", or "Spam".
Sometimes it may happen that such a situation repeats and for a few days in a row some percentage of emails stay in the "Undelivered" section. In this case, feel free to reach out to our customer success team and they will help you to understand why it's happening and resolve the issue.
Why your emails are not delivered?
There might be different issues behind the delivery issues:
wrong DNS records
service that you use is not added to the SPF
absence of the DKIM key
wrong DMARC record
the conflict between DNS records
the bad reputation of the inbox
low sender score of the IP