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description: Reasons due to which your email campaign may go undelivered.
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# Why Email Notification may not get delivered?

There are several reasons for which you may not be able to deliver your Email Notifications:

<figure><img src="https://1782533751-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FazJDZwzHkmWIbkYOetQH%2Fuploads%2FLSOSHLh0CLlREePX4Y9v%2FEmail_Push_Horizontal_Creative.png?alt=media&#x26;token=99cb765e-21d2-4f3f-ba56-c49311431f94" alt=""><figcaption><p>Reasons why your Email Notification is not delivered</p></figcaption></figure>

* **Frequency Caps:** This failure occurs when the frequency cap limit is exhausted. It depends on parameters that are measured daily, weekly, monthly, or over a lifetime. Users whose frequency cap value is >0 will receive your engagement. To learn more about Frequency Caps, click [here](../../getting-started#frequency-caps).
* **Personalization Failure:** This failure indicates that the engagement failed to send while replacing the personalizing parameters with the actual value stored in the users profile.\
  **Use Case:** Suppose there is a user in a segment with no premium amount registered. You create engagement for that segment of users using a premium amount macro with an expiration date. The user with no registered amount will not receive the engagement as that parameter does not exist in his/her stored profile.
* **Hard Bounce:** Hard bounce events from ESP will be displayed here, when they occur for a particular email. When it comes to sending emails, bounces are a pretty common metric, so it will be shown separately as a reason. If we receive a hard bounce, it means that either the address is invalid or the person has blocked the sender. Therefore, the user's email address must be marked as unreachable for further communications.&#x20;
* **Dropped:** The majority of ESPs report dropped events. An email maybe dropped because the user unsubscribes or is on the blacklist.&#x20;
* **Soft Bounce:** Soft bounces indicate temporary failures. ESPs report soft bounce as a separate event in webhook.
* **Insufficient Credits:** If the ESP quota limit has been reached or there are not enough credits available with the client, it will fall in this category.
* **Vendor Failure:** Other than the above reasons, all other reasons why the vendor sends failures will be listed here. Backend systems should keep raw logs of the response that we received in case further analysis is asked by the client. In the future, we will also display different vendor failure reasons in the UI. The logs will be kept for 2 years.
* **Non 2xx Response:** A vendor may log any other error in addition to ones listed.
* **Pending status from Vendor:** This failure bucket applies to the situation where we sent the communication to the vendor, but the vendor did not send a webhook communication for the message ID.
* **Others:** This includes all the other reasons for which the Email was not delivered such as system failure, server crash, campaign failure, etc.
