> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://support.promo.ly/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# Bounced emails

When an email promo cannot be delivered to an email address, it’s called a bounce. There are lots of different reasons why promos can bounce so, when it happens, a “return to sender” message (or, SMTP reply) is sent from the recipient’s mail server to explain why. Promo.ly will display this information in your activity log. We recommend reading this support article about free list [analysis](http://support.promo.ly/knowledge-base/free-list-analysis/).