When an email is rejected by a user's email service, the message is considered bounced. There are two distinct types of bounces, hard bounces and soft bounces.
Hard bounces indicate that the message permanently cannot be delivered. This could be due to the email address not existing, the domain being invalid, or the email server rejecting all messages.
Soft bounces indicate a temporary delivery issue. This could be due to spam issues, a mailbox being full, the email server being down and more.
When an email is sent from Mixpanel and it bounces, then a "Bounce Category" property will be automatically set on a user's profile. Below is a list of the "Bounce Category" values and what each error code represents:
- Bad-domain: the domain of the email address (for example '@gnail.com') is not valid
- Bad-mailbox: the email address doesn’t exist on the server
- Inactive-mailbox: the email address used to exist but has become deactivated
- Invalid-sender: that the receiving domain does not like the ip/domain sending the email
- Policy-related: a catch-all category, often indicating the sender is on a blacklist
- Relaying-issues: the mail is being relayed and errors out
- Routing-errors: the mail is being routed and there are fatal errors
- Spam-related: the receiving mail provider believes either the content or sender of this content is a spammer.