BOING!
That was the sound of your email bouncing.
As a publisher, or anyone involved in email marketing, you might feel there is no worse sound. Except there is. It’s the sound of silence.
It’s the silence of your email never even reaching the recipient’s servers - or reaching the mailbox, and being swiftly and silently escorted to the spam folder by the automatic filters. Because there was no BOING! - you never know.
The percentage of sent emails that actually make it to the inbox (your deliverability rate), is the metric by which email campaigns and email newsletters live or die. It’s not just related to that one email, either. One email campaign with outstandingly bad deliverability (think 40-50% of your emails never made it to their destination) and your future campaigns start with a mark against them.