When an email message cannot be delivered to an address, a response is sent back from the receiving server. Based on an evaluation of the response, the bounce is considered either a hard or soft bounce.
What is a hard bounce?
When the response from the receiving server indicates that the address is invalid (examples: "user unknown", "no such user here", "invalid recipient", etc...), the bounce is classified as a hard bounce.
What is a soft bounce?
When the response from the receiving server indicates that the address is valid (examples: "mail box full", "temporary fail", "spam block") the bounce is classified as a soft bounce.
When is a contact's email address marked as "invalid" by Cordial?
After the first hard bounce.
After 6 or more consecutive soft bounces have occurred across a timeframe of at least 21 days.
Note: multiple soft bounces received within a 24 hour period only increases the total count by 1.
Note: If less than 21 days (3 weeks) have passed during a string of consecutive soft bounces, the contact is not marked as invalid. Once the pattern has occurred for more than 3 weeks (at least 6 times in a row without a successful send), the address will be deemed undeliverable and marked as "invalid".
How are email addresses marked as "invalid" handled?
Any address marked as invalid are automatically suppressed from any message send.
Addresses marked as invalid are NOT included in the audience count total when building an audience for an email message.
Addresses marked as invalid are included in the audience count total when searching for contacts in the "search" outside of the message creation process.
Am I able to identify and correct issues with an email addresses that has been marked as invalid?
While it is possible to update a subscriber from invalid to valid status using the api call PUT <path>/contacts that is described below, it is also necessary, if the contact was invalidated due to a "hard" bounce, to contact Cordial support and request that the contact be removed from any MTA suppression lists.
You can overwrite the invalid setting by making a PUT call for the contact record via the REST API. This should only be done when the email address was marked as invalid due to a typo (examples: "user unknown", "no such user here", "invalid recipient", etc...) and the email address is also corrected during the PUT.