# Undelivered Email

*Email Deliverability*. A category of reasons why an email address wasn't sent to a recipient's inbox. These reasons cover issues with email address or email message content.

Once an email send attempt fails, a couple of things can happen to your email:

* [Bounced][]. Recipient email server rejects an email message sent to this recipient's email address.
* Marked as [Spam][]. The recipient marked this email message as spam.
* [Dropped][]. The recipient had been added to a [suppression list][].
* Set as [Invalid][]. The recipient email address doesn't exist.

[Bounced]: /docs/sendgrid/glossary/bounces

[spam]: /docs/sendgrid/glossary/spam

[Dropped]: /docs/sendgrid/glossary/drops

[Invalid]: /docs/sendgrid/glossary/invalid-email

[suppression list]: /docs/sendgrid/ui/sending-email/index-suppressions